Authors: Liu, Y. W., Wu, K. Y., Hsu, Y. L.; recommended: Yeh-Liang Hsu
Note: This paper is presented at 2012 International Society of
Gerontechnology World Conference, Technische Universiteit Eindhoven (TU/e), the
Netherlands, June 26~29, 2012. This paper is also published at Gerontechnology 2012; 11(2): 255; doi: 10.4017/gt.2012.11.02.590.00
An integrated motion sensing mattress for elderly living
people living in homes or nursing homes, the bed is an indispensable part of
their daily lives. Bed activity monitoring provides valuable information of the
status of the elderly people. Various sensors have been implemented for this purpose,
such as static charge sensitive bed, force sensors,
air cushion, and textile-based sensors. This paper
presents the development of an integrated sensing mattress, “SmartPad”, for
unobtrusive sensing of physical activities in the bed. Working with a bedding
manufacturer, this research aims to design a mattress with motion sensing
capability using the same material and fabrication process of the bedding
manufacturer, so that the mattress is comfortable, washable, inexpensive, and
is closer to being a commercial product.
SmartPad is in a
sandwich structure of two pieces of foam 6~10mm in thickness, on which conductive fiber is
knitted in a special pattern in the “sensing area”, with pieces of conductive
fabric in between. As shown in Figure 1, the average resistance of 10 tests of
a 20cm×20cm sensing area decreases monotonically with
applied pressure in the range of 500-3,500Pa (equivalent to pressure caused by
the presence of an adult). The special elastic foam provided by the bedding
manufacture has passed the fatigue test of 30,000 pressure cycles. Figure 2
shows a possible layout of the mattress, with 3 horizontal sensing areas for
detecting movements of the upper limbs, hip and lower limbs, and 3 vertical areas for detecting movements of the trunk.
Figure 1. Applied pressure vs. resistance
Figure 2. Pressure sensing units on the SmartPad
Results & Discussion
information systems, SmartPad was successfully implemented in the nursing homes
to facilitate real-time monitoring of on/off bed status, sleep posture and body
movements, using 10 Hz sampling rate of the resistance. Service reminders and
history reports were also provided. Various living assistance applications are developed, such as detecting sitting
posture changes on a wheelchair, motion sensing carpet for monitoring purposes,
and a “touch and call” pad for elderly people with impaired motor skills who
cannot handle the usual press buttons.
activity monitoring, pressure
sensing, living assistance.
et. al, “Use of the SCSB method for monitoring of respiration, body movements
and ballistocardiogram in infants”, Early
Human Development, 1984, v. 9, n. 2, pp. 119-126.
 Brink et. al, “Contact-free
measurement of heart rate, respiration rate, and body movements during sleep”, Behavior
Research Methods, 2006, v. 38, n. 3, pp. 511-521.
et. al, “Noninvasive measurement of heartbeat, respiration, snoring and body
movements of a subject in bed via a pneumatic method”, Biomedical Engineering, 2005, v. 52, pp. 2100-2107.
et. al, “Development of a portable device for tele-monitoring of physical
activities during sleep", Telemedicine
and e-Health, 2008, v. 14, n. 10, pp. 1044-1056.
 Liu et. al, “Development of a Care
Management System for Nursing Homes based on SmartPad”, 1st Asia Pacific eCare
and TeleCare Congress, June, 2011, Hong Kong, China.