INTRODUCTION
The ability to accurately monitor a person’s body movements
during sleep can enable an array of applications, ranging
from sleep monitoring to abnormal body movements detection,
such as restless legs. A number of bed-mounted sensing systems
have been proposed for this purpose, including pressure
sensors [14], [18], temperature sensors [19], ultrasound sensors
[30], load cell sensors [6] and custom-made sensors [9].
Among these sensors, load cells have been shown to provide
a viable solution for several reasons. Firstly, load cells are
very affordable and readily available. Secondly, deploying a
load cell based system can be very conveniently done, without
interfering with the bed or how it is currently used. Thirdly,
load cells (when placed under the bed legs) can easily capture
the changes in body weight distribution caused by movements,
especially when the movements are rather noticeable. As a
result, we believe that load cells could potentially offer a
practical approach to on-bed body movement monitoring.
Even though earlier studies point out that low-end load
cells can be integrated to beds to detect some large body