System and method for detecting transitions between sitting and standing states

摘要

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.

主权项

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 for at least first, second and third axes over a period of time, determining, by a microprocessor, a plurality of points of approximate acceleration magnitude, which comprises determining, at each of the plurality of points of accelerometer data, a difference between an acceleration vector magnitude and a value for an acceleration due to gravity, wherein the acceleration vector magnitude is a vector magnitude of accelerometer data for the first, second, and third axes at a point in time, determining, by the microprocessor, a plurality of points of velocity vector magnitude from the plurality of points of approximate acceleration magnitude, determining, by the microprocessor, a segment comprising selecting a first point in time of the velocity vector magnitude and a second point in time of the velocity vector magnitude that satisfy at least a condition that a length of the segment is within a predetermined range and a condition that the first point in time of the velocity vector magnitude and the second point in time of the velocity vector magnitude are below a threshold of user motion, wherein the first point in time and the second point in time correspond to beginning and end points of the segment, respectively, for each of the first and second points in time:
setting, by the microprocessor, the threshold of user motion to be a first predetermined value if a user motion at the respective point is less than a predetermined motion limit,setting, by the microprocessor, the threshold of user motion to be a second predetermined value if the user motion at the respective point is greater than or equal to the predetermined motion limit, andwherein determining the condition that the first point in time of the velocity vector magnitude and the second point in time of the velocity vector magnitude are below the threshold of user motion is determining, by the microprocessor, that a degree of the user motion over a neighboring period of time ending at the respective point is less than the set threshold of user motion, correcting, by the microprocessor, the plurality of points of velocity vector magnitude within the segment, determining, by the microprocessor, a plurality of points of vertical displacement for the corrected plurality of points of velocity vector magnitude, and detecting, by the microprocessor, that the user has transitioned between the sitting and standing states from a comparison of a vertical displacement at the first point in time and a vertical displacement at the second point in time.