Biomedical Engineering Reference
In-Depth Information
notably proprioceptive feedback from the legs and vestibular feedback. Fortunately,
more natural locomotion interfaces, such as bicycles, treadmills and fully-tracked
free-walking spaces, are becoming more common (see [
24
] for a review). Although
with these solutions locomotion is much closer to real life movements, they are still
constrained in important ways. In the case of the bicycle, for instance, there is no
absolute one-to-one relationship between the metrics of visual space and those of
the proprioceptive movements because of the unknown scale of one pedal rotation
(i.e., this would depend on the gear, for instance). Fully-tracked walking spaces are
constrained by the size of the actual space within which they are contained. Treadmill
setups are restrictive as most of them are rather small [
94
] and only allow walking
in one direction. Indeed, in everyday navigational tasks, we rarely walk completely
straight over extended periods of time. In short, today it is still difficult to allow
people to freely walk through large scale VEs in an unconstrained manner.
It is this unsatisfactory situation that prompted some of the work reported in this
volume and it likewise prompted the CyberWalk project. The goal of this project
was the development of a novel, multimodal, omnidirectional walking interface,
with at its core, a 4
4 m omnidirectional treadmill. The project encompassed
an international consortium dedicated to both scientific and technological research.
The CyberWalk platform is the first truly omnidirectional treadmill of its size that
allows for natural walking in any direction through arbitrarily large Virtual Environ-
ments. It is a major step towards having a single setup that allows for the study of
the many facets of human locomotion, ranging from the biomechanical to the cogni-
tive processes involved in navigating large areas. The platform consists of segmented
belts which are mounted on two large chains in the shape of a torus, which allows it to
move the walking surface in both horizontal directions and thereby enables indefinite
omnidirectional walking and turning (see Fig.
6.7
). It is integrated with additional
VR capabilities so that a virtual world is presented through a head-mounted display
(HMD) and updated as a function of the movements of the user. The platform is
described more fully in [
95
] and in Sect.
6.5
of this chapter. More detailed descrip-
tions of specific technological and engineering aspects of the platform can be found
elsewhere [
29
,
87
-
89
,
94
,
112
].
The technological development of the platform had a strong human-centered
approach and was guided by human gait and psychophysical research conducted
at the Max Planck Institute for Biological Cybernetics (MPI), one of the consortium
partners. Here we report on a selected number of these studies. Since a major objec-
tive was to develop a platform that enables natural walking, we studied basic gait
parameters during natural unconstrained outdoor walking as a general reference. The
CyberWalk platform has at its core a treadmill, and thus we investigated potential dif-
ferences between normal overground walking and treadmill walking. Studies were
also focused on the multisensory processes at play during human walking. While
there is a wealth of research on the role of vision in locomotion, relatively little is
known about the interaction between the different non-visual senses. Consequently,
a series of studies was conducted to look at the interaction between vestibular and
proprioceptive information during walking. Finally, a number of studies on human
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