Ambulatory system for measuring and monitoring physical activity and risk of falling and for automatic fall detection
First Claim
1. A body movement monitoring system comprising:
- a data processing system comprising one or more processor circuits, said data processing system configured to process acceleration measurements generated by a sensor, the sensor adapted to be attached to an upper part of a body of a person and comprising at least one accelerometer component adapted to generate one or more acceleration signals in response to movement of the body, the data processing system programmed to;
apply a filter to at least a portion of at least one of the one or more acceleration signals to obtain one or more filtered signals;
determine an estimated postural transition duration for a postural transition based at least partly on one or more peaks in the one or more filtered signals;
derive information related to the postural transition using the estimated postural transition duration, the information including at least one of;
time of occurrence of the postural transition, duration of the postural transition, or type of the postural transition;
apply a filter to a vertical accelerometer signal of the one or more acceleration signals for a time period corresponding to said duration of said postural transition, to obtain a filtered vertical acceleration signal;
compute a gradient of the filtered vertical acceleration signal to obtain a gradient signal;
identify a global extremum of said gradient signal;
if the magnitude of the global extremum exceeds a threshold value, compare a first portion of the filtered vertical acceleration signal that precedes the global extremum to a second portion of the filtered vertical acceleration signal that is subsequent to the global extremum;
if said comparison yields a first result, identify a lying posture; and
if said comparison yields a second result, identify a transition from said lying posture.
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Accused Products
Abstract
The present invention relates to a light-weight, small and portable ambulatory sensor for measuring and monitoring a person'"'"'s physical activity. Based on these measurements and computations, the invented system quantifies the subject'"'"'s physical activity, quantifies the subject'"'"'s gait, determines his or her risk of falling, and automatically detects falls. The invention combines the features of portability, high autonomy, and real-time computational capacity. High autonomy is achieved by using only accelerometers, which have low power consumption rates as compared with gyroscope-based systems. Accelerometer measurements, however, contain significant amounts of noise, which must be removed before further analysis. The invention therefore uses novel time-frequency filters to denoise the measurements, and in conjunction with biomechanical models of human movement, perform the requisite computations, which may also be done in real time.
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Citations
27 Claims
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1. A body movement monitoring system comprising:
a data processing system comprising one or more processor circuits, said data processing system configured to process acceleration measurements generated by a sensor, the sensor adapted to be attached to an upper part of a body of a person and comprising at least one accelerometer component adapted to generate one or more acceleration signals in response to movement of the body, the data processing system programmed to; apply a filter to at least a portion of at least one of the one or more acceleration signals to obtain one or more filtered signals; determine an estimated postural transition duration for a postural transition based at least partly on one or more peaks in the one or more filtered signals; derive information related to the postural transition using the estimated postural transition duration, the information including at least one of;
time of occurrence of the postural transition, duration of the postural transition, or type of the postural transition;apply a filter to a vertical accelerometer signal of the one or more acceleration signals for a time period corresponding to said duration of said postural transition, to obtain a filtered vertical acceleration signal; compute a gradient of the filtered vertical acceleration signal to obtain a gradient signal; identify a global extremum of said gradient signal; if the magnitude of the global extremum exceeds a threshold value, compare a first portion of the filtered vertical acceleration signal that precedes the global extremum to a second portion of the filtered vertical acceleration signal that is subsequent to the global extremum; if said comparison yields a first result, identify a lying posture; and if said comparison yields a second result, identify a transition from said lying posture. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A method for monitoring body movement, the method comprising:
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receiving acceleration measurements corresponding to one or more acceleration signals generated by at least one accelerometer component of a sensor unit attached to an upper part of a body of a person in response to movement of the body; with a data processing system comprising one or more processor circuits; applying a filter to at least a portion of at least one of the one or more acceleration signals to obtain one or more filtered signals; determining an estimated postural transition duration for a postural transition based at least partly on one or more peaks in the one or more filtered signals; deriving information related to the postural transition using the estimated postural transition duration, the information including at least one of;
time of occurrence of the postural transition, duration of the postural transition, or type of the postural transition;determining a revised estimated postural transition duration that is more accurate than the estimated postural transition duration; and deriving at least part of the information by estimating an acceleration of the person during a time period corresponding to the revised estimated postural transition duration, said estimating comprising; processing a frontal acceleration signal of the one or more acceleration signals to correct for a sagittal trunk tilt angle of the person during the time period corresponding to the revised estimated postural transition duration to obtain a corrected frontal acceleration signal; using the corrected frontal acceleration signal and a vertical acceleration signal of the one or more acceleration signals, estimating time-varying inertial frontal and vertical acceleration signals; removing a gravitational component from the estimated time-varying inertial vertical acceleration signal; computing a time-varying magnitude signal corresponding to a square root of a sum of squares of said estimated time-varying inertial frontal and vertical acceleration signals; applying at least one filter to said time-varying magnitude signal to obtain a filtered time-varying magnitude signal; identifying a local extremum in said filtered time-varying magnitude signal preceding the time of occurrence of said postural transition (P_pre); and identifying a local extremum in said filtered time-varying magnitude signal following the time of occurrence of said postural transition (P_post). - View Dependent Claims (25, 26)
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27. Non-transitory computer storage that stores executable code that directs a computer system to at least:
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apply a filter to at least a portion of at least one of one or more acceleration signals generated by at least one accelerometer component of a sensor unit attached to an upper part of a body of a person, the one or more acceleration signals generated in response to movement of the body; determine an estimated postural transition duration for a postural transition based at least partly on one or more peaks in the at least a portion of the one or more acceleration signals that is filtered; using the estimated postural transition duration, derive information related to the postural transition, the information including at least one of;
time of occurrence of the postural transition, duration of the postural transition, or type of the postural transition;apply a filter to a vertical accelerometer signal of the one or more acceleration signals for a time period corresponding to said duration of said postural transition, to obtain a filtered vertical acceleration signal; compute a gradient of the filtered vertical acceleration signal to obtain a gradient signal; identify a global extremum of said gradient signal; if the magnitude of the global extremum exceeds a threshold value, compare a first portion of the filtered vertical acceleration signal that precedes the global extremum to a second portion of the filtered vertical acceleration signal that is subsequent to the global extremum; if said comparison yields a first result, identify a lying posture; and if said comparison yields a second result, identify a transition from said lying posture.
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Specification