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Smartphone based fall detection system
Stefan Madansingh,Timothy A. Thrasher,Charles S. Layne,Beom-Chan Lee 제어로봇시스템학회 2015 제어로봇시스템학회 국제학술대회 논문집 Vol.2015 No.10
This paper describes the design of a smartphone based fall detection system and characterizes the preliminary efficacy of the proposed system in activities of daily living (ADLs). Using the embedded sensors available in a smartphone (i.e., accelerometer, gyroscope and magnetometer), kinematic analysis of movement can be performed in real-time, allowing for continuous monitoring of fall status. Fall sensing thresholds are defined based on angular rate of change (TH1), maximum acceleration (TH2), and maximum attitude change (TH3). TH1 is measured from the resultant pitch and roll angular velocity vector and defined as 3.1 rad/s (~180°/s). TH2 is measured from the resultant acceleration vector and defined as 1.6 g. TH3 is measured from the resultant vector of the pitch and roll angles, and defined at 0.59 rad (39°). A proof-of-concept study was performed on five ADL tasks: 1) comfortable walking, 2) stand-to-seated posture, 3) seated-to-standing posture, 4) pivoting at the waist to pick up an object, and 5) stand-to-seated-to-laying transition. No trials violated the defined thresholds for fall detection, signifying no false positives. These results are important for the definition of machine learning algorithms, currently under development, to minimize false positive and false negative fall detection events.
Lee, Beom-Chan,Fung, Alberto,Thrasher, Timothy A. IEEE 2018 IEEE transactions on neural systems and rehabilita Vol.26 No.1
<P>Coding scheme for earlier versions of vibrotactile biofeedback systems for balance-related applications was primarily binary in nature, either on or off at a given threshold (range of postural tilt), making it unable to convey information about error magnitude. The purpose of this paper was to explore the effects of two coding schemes (binary versus continuous) for vibrotactile biofeedback during dynamic weight-shifting exercises that are common physical therapists’ recommended balance exercises used in clinical settings. Nine individuals with idiopathic Parkinson’s disease and nine healthy elderly individuals participated in this paper. All participants performed dynamic weight-shifting exercises assisted with either the binary or continuous vibrotactile biofeedback delivered using with vibrating actuators (tactors) in either the anterior–posterior or medial–lateral direction. Participants’ limits of stability at pre and post exercises were compared to evaluate the effects of the exercises on their range of motion. The continuous coding scheme produced significantly better performance than the binary scheme when both groups were performing dynamic weight-shifting balance exercises with assistive vibrotactile biofeedback. The results have implications in terms of maximizing the effects of error-driven motor learning and increasing performance on balance rehabilitation training combined with vibrotactile biofeedback.</P>