Biomedical Engineering Reference
In-Depth Information
applications such as biometric authentication. Mostayed et al. studied the recogni-
tion of walker identity from ground-reaction force profiles acquired through a force
plate [
22
], as did Headon and Curwen [
13
]. A further promising application in this
area is the early identification of at-risk gait in aging populations from foot-ground
force measurements. Holtzreiter and Kohle [
17
] were among the first to employ
machine learning techniques to identify normal and pathological gait patterns from
force platform recordings.
17.3.2.1 Under-Floor Camera-Projector Systems
Another method that has been used to enable foot-floor interactions with visual feed-
back employs under-floor cameras and projectors to render interactions via translu-
cent floor plates. Groenboek et al. implemented an interactive floor surface called the
iGameFloor using body gestures sensed optically through translucent floor plates,
which were also used to display visual feedback via rear-projected video [
12
]. Four
projectors and cameras were installed in a cavity beneath floor level, creating an
interactive floor area 3
4 m in size. The locations of limbs near to the interac-
tive surface were tracked, and were used to mediate interactions with multi-person
floor-based video games.
Augsten et al. adapted the method of optical sensing via frustrated total internal
reflection to enable the dynamic capture of foot-floor contact areas through back-
projected translucent floor plates [
4
]. This method provides direct imaging of contact
area, although it does not directly reveal forces. The main drawback to this approach
is that it requires the installation of cameras and projectors within a potentially
large recessed space that must be available beneath the floor. The authors imple-
mented and evaluated the usability of foot-floor touch-surface interfaces using this
approach (Fig.
17.4
). Similar to the methods described in Sect.
17.4.1
, they identi-
fied salient selection points within the foot-floor contact interface in order to enable
precision pointing to targets or performance of other actions through a floor-based
touch-screen interface.
×
17.3.3 Usability
A number of special considerations can be identified in relation to the usability of
touch surfaces designed for the feet, including the appropriate size, distance, and
arrangement of control areas, the type of gestures suitable for use with the feet, and
the respective role of each foot during interaction, among others. Similar to the case of
hand-based touch-surface interaction, the appropriate size of controls for use with the
feet likely depends on a range of factors, including limitations in sensing resolution,
user motor abilities, and feedback modalities. Such factors have been studied in the
literature on task performance in human-computer interaction generally [
18
,
21
] and
on touch-screen usability in particular [
3
,
6
], where the appropriate size of controls
