SYSTEM AND METHOD FOR DETECTING TRANSITIONS BETWEEN SITTING AND STANDING STATES

• US 20140364769A1
• Filed: 06/07/2013
• Published: 12/11/2014
• Est. Priority Date: 06/07/2013
• Status: Active Grant

• Current Assignee: Seismic Holdings, Inc. (SRI International, Inc.)
• Original Assignee: LUMO BodyTech, Inc.
• Inventors: Chang, Andrew Robert, Hauenstein, Andreas Martin
• Granted Patent: US 9,591,996 B2
• Time in Patent Office: Days
• US Class Current: 600/595
• CPC Class Codes: A61B 5/0022 Monitoring a patient using a global network, e.g. telephone networks, internet
• CPC Class Codes: A61B 5/1116 Determining posture transitions
• CPC Class Codes: A61B 5/1126 using a particular sensing technique
• CPC Class Codes: A61B 5/6814 Head
• CPC Class Codes: A61B 5/6822 Neck
• CPC Class Codes: A61B 5/6823 Trunk, e.g., chest, back, abdomen, hip
• CPC Class Codes: G01P 15/18 in two or more dimensions

Abstract

A system and method are described herein for detecting a user'"'"'s transition between sitting and standing postures. Transitions between sitting and standing states are reliably detected using an accelerometer attached to the user. By modeling error introduced by the accelerometer, and correcting for this error, transitions between sitting and standing states are reliably detected. A microprocessor coupled to the accelerometer converts the captured accelerometer data to approximate vertical acceleration. Vertical velocity, which includes accelerometer error, is determined from the approximate vertical acceleration. The vertical velocity is corrected, and the corrected vertical velocity used to determine vertical displacement. Transitions between sitting and standing states are determined from the vertical displacement.

Claims

1. A method of detecting a user transition between sitting and standing states comprising:

capturing, by a tri-axial accelerometer attached to a user, a plurality of points of accelerometer data over a period of time,

determining, by a microprocessor, a plurality of points of approximate vertical acceleration due to user motion from the plurality of points of accelerometer data,

determining, by the microprocessor, a plurality of points of vertical velocity from the plurality of points of approximate vertical acceleration due to user motion,

segmenting, by the microprocessor, the plurality of points of vertical velocity,

correcting, by the microprocessor, each of the segments of points of vertical velocity,

determining, by the microprocessor, a segment of points of vertical displacement for each corrected segment of points of vertical velocity, and

detecting, by the microprocessor, a user transition between sitting and standing states from the segments of points of vertical displacement.

2. The method of claim 1 where determining the plurality of points of approximate vertical acceleration due to user motion from the plurality of points of accelerometer data comprises:

determining, by the microprocessor, a magnitude of each of the plurality of points of accelerometer data, and

subtracting, by the microprocessor, a value for an acceleration due to gravity from the magnitude of each of the plurality of points of accelerometer data.

3. The method of claim 2 further comprising:

determining, by the microprocessor, a running average of the magnitude of each of the plurality of points of accelerometer data, and

periodically updating, by the microprocessor, the value for the acceleration due to gravity using the running average of the magnitude of each of the plurality of points of accelerometer data.

4. The method of claim 1 where segmenting the plurality of points of vertical velocity comprises:

selecting, by the microprocessor, a first point of the plurality of points of vertical velocity as a beginning of a segment, and

selecting, by the microprocessor, a second point of the plurality of points of vertical velocity as an end of the segment,

wherein the segment contains a number of points of the plurality of points of vertical velocity, and

determining that a minimal amount of user motion is present at the first and second points,

5. The method of claim 4 where determining that a minimal amount of user motion is present at the first and second points comprises determining that the approximate vertical acceleration due to user motion at the first and second points is close to zero.

6. The method of claim 4 where determining that a minimal amount of user motion is present at the first and second points comprises, for each of the first and second points:

setting a motion threshold to be a first predetermined value if a user motion at the point is less than a predetermined motion limit,

setting the motion threshold to be a second predetermined value if the user motion at the point is greater than or equal to the predetermined motion limit, and

determining that a degree of user motion over a neighboring period of time ending at the point is less than the set motion threshold.

7. The method of claim 1 where correcting each of the segments of points of vertical velocity comprises:

determining, by the microprocessor, a linear error for each of the segments of points of vertical velocity, and

removing, by the microprocessor, the linear error from each of the segments of points of vertical velocity.

8. The method of claim 1 where detecting a user transition between sitting and standing states from the segments of points of vertical displacement comprises:

determining, by the microprocessor, a change in vertical displacement from a first point of vertical displacement at a beginning of a segment in one of the segments of points of vertical displacement to a second point of vertical displacement at an end of the segment in one of the segments of points of vertical displacement,

detecting, by the microprocessor, a transition between sitting and standing states when the change in vertical displacement is positive and greater than a predefined limit, and

detecting, by the microprocessor, a transition between standing and sitting states when the change in vertical displacement is negative and less than the predefined limit.

9. An apparatus for detecting a user transition between sitting and standing states comprising:

a tri-axial accelerometer attached to a user configured to capture a plurality of points of accelerometer data over a period of time, and

a microprocessor, coupled to the tri-axial accelerometer, the microprocessor configured to;

determine a plurality of points of approximate vertical acceleration due to user motion from the plurality of points of accelerometer data,

determine a plurality of points of vertical velocity from the plurality of points of approximate vertical acceleration due to user motion,

segment the plurality of points of vertical velocity,

correct each of the segments of points of vertical velocity,

determine a segment of points of vertical displacement for each corrected segment of points of vertical velocity, and

detect a user transition between sitting and standing states from the segments of points of vertical displacement.

10. The apparatus of claim 9 where the microprocessor is configured to determine the plurality of points of approximate vertical acceleration due to user motion from the plurality of points of accelerometer data by being configured to:

determine a magnitude of each of the plurality of points of accelerometer data, and

subtract a value for an acceleration due to gravity from the magnitude of each of the plurality of points of accelerometer data.

11. The apparatus of claim 10 where the microprocessor is further configured to:

determine a running average of the magnitude of each of the plurality of points of accelerometer data, and

periodically update the value for the acceleration due to gravity using the running average of the magnitude of each of the plurality of points of accelerometer data.

12. The apparatus of claim 9 where the microprocessor is configured to segment the plurality of points of vertical velocity by being configured to:

select a first point of the plurality of points of vertical velocity as a beginning of a segment, and

select a second point of the plurality of points of vertical velocity as an end of the segment,

wherein the segment contains a number of points of the plurality of points of vertical velocity, and

determine that a minimal amount of user motion is present at the first and second points.

13. The apparatus of claim 12, where the microprocessor is configured to determine that a minimal amount of user motion is present at the first and second points by being configured to determine that the vertical acceleration due to user motion at the first and second points is close to zero.

14. The apparatus of claim 12, where the microprocessor is configured to determine that a minimal amount of user motion is present at the first and second points by being configured to, for each of the first and second points:

set a motion threshold to be a first predetermined value if a user motion at the point is less than a predetermined motion limit,

set the motion threshold to be a second predetermined value if the user motion at the point is greater than or equal to the predetermined motion limit, and

determine that a degree of user motion over a neighboring period of time ending at the point is less than the set motion threshold.

15. The apparatus of claim 9 where the microprocessor is configured to correct the segments of points of vertical velocity by being configured to:

determine a linear error for each segment of points of vertical velocity, and

remove the linear error from each segment of points of vertical velocity.

16. The apparatus of claim 9 where the microprocessor is configured to detect a user transition between sitting and standing states from the segments of vertical displacement by being configured to:

determine a change in vertical displacement from a first point of vertical displacement at a beginning of a segment in one of the segments of points of vertical displacement to a second point of vertical displacement at an end of the segment in one of the segments of points of vertical displacement,

detecting a transition between sitting and standing states when the change in vertical displacement is positive and greater than a predefined limit, and

detecting a transition between standing and sitting states when the change in vertical displacement is negative and less than the predefined limit.

17. A non-transitory computer readable medium having stored thereupon computing instructions comprising:

a code segment to capture from a tri-axial accelerometer attached to a user a plurality of points of accelerometer data over a period of time,

a code segment to determine a plurality of points of approximate vertical acceleration due to user motion from the plurality of points of accelerometer data,

a code segment to determine a plurality of points of vertical velocity from the plurality of points of approximate vertical acceleration due to user motion,

a code segment to segment the plurality of points of vertical velocity,

a code segment to correct each of the segments of points of vertical velocity,

a code segment to determine a segment of points of vertical displacement for each corrected segment of points of vertical velocity, and

a code segment to detect a user transition between sitting and standing states from the segments of points of vertical displacement.

18. The non-transitory computer readable medium of claim 17 where the code segment to determine the plurality of points of approximate vertical acceleration due to user motion from the plurality of points of accelerometer data further comprises:

a code segment to determine a magnitude of each of the plurality of points of accelerometer data, and

a code segment to subtract a value for an acceleration due to gravity from the magnitude of each of the plurality of points of accelerometer data.

19. The non-transitory computer readable medium of claim 18 further comprising:

a code segment to determine a running average of the magnitude of each of the plurality of points of accelerometer data, and

a code segment to periodically update the value for the acceleration due to gravity using the running average of the magnitude of each of the plurality of points of accelerometer data.

20. The non-transitory computer readable medium of claim 17 where the code segment to segment the plurality of points of vertical velocity further comprises:

a code segment to select a first point of the plurality of points of vertical velocity as a beginning of a segment, and to select a second point of the plurality of points of vertical velocity as an end of the segment,

wherein the segment contains a number of points of the plurality of points of vertical velocity, and

determine that a minimal amount of user motion is present at the first and second points.

21. The non-transitory computer readable medium of claim 20 where the code segment to determine that a minimal amount of user motion is present at the first and second points further comprises a code segment to determine that the vertical acceleration due to user motion at the first and second points is close to zero.

22. The non-transitory computer readable medium of claim 20 where the code segment to determine that a minimal amount of user motion is present at the first and second points further comprises a code segment to, for each of the first and second points:

set a motion threshold to be a first predetermined value if a user motion at the point is less than a predetermined motion limit,

set the motion threshold to be a second predetermined value if the user motion at the point is greater than or equal to the predetermined motion limit, and

determine that a degree of user motion over a neighboring period of time ending at the point is less than the set motion threshold.

23. The non-transitory computer readable medium of claim 17 where the code segment to correct each of the segments of points of vertical velocity further comprises:

a code segment to determine a linear error for each of the segments of points of vertical velocity, and

a code segment to remove the linear error from each of the segment of points of vertical velocity.

24. The non-transitory computer readable medium of claim 17 where the code segment to detect a user transition between sitting and standing states from the segments of points of vertical displacement comprises:

a code segment to determine a change in vertical displacement from a first point of vertical displacement at the beginning of a segment in one of the segments of points of vertical displacement to a second point of vertical displacement at an end of the segment in one of the segments of points of vertical displacement,

a code segment to detect a transition between sitting and standing states when the change in vertical displacement is positive and greater than a predefined limit, and

a code segment to detect a transition between standing and sitting states when the change in vertical displacement is negative and less than the predefined limit.