Biomedical Engineering Reference
In-Depth Information
connected to the ceiling to prevent them from falling and reaching the edge of the
platform with their feet.
The setup is installed in a large hall (12
12mwalking area). The hall is equipped
with a 16 camera Vicon MX13 optical tracking system (Vicon, Oxford, United
Kingdom) that is used to track the position and orientation of the participant's head.
To this end, participants wear a helmet with reflective markers. The tracking data are
used to update the visualization presented through a head-mounted display (HMD)
and to control the treadmill velocity. Presently the HMD used is an eMagin Z800
3DVisor (eMagin, Bellevue, USA) custom built into goggles, which prevents the
participant from seeing anything else but the image on the displays. One advantage
of this HMD is that it is lighter (
×
227g) and less obtrusive than most other HMD
systems, but also has a reduced field-of-view. If required, user responses can be col-
lected via a wireless gamepad. When not in use, the treadmill can be covered with
wooden boards with a thick rubber coating, creating one continuous, fully tracked
walking area.
The omnidirectional capabilities of the platform form its largest contribution to the
scientific study of human walking biomechanics. By definition, locomotion serves
to transport us from one place to another. However, one of the major constraints on
research has been space. For a typical research facility it is extremely expensive to
maintain, and difficult to justify, a large instrumented, but otherwise empty room.
Most locomotion laboratories are therefore rather small, especially in comparison
to the scale of real walking. There is of course a relatively simple solution to the
space limitation, and that is to put the participant on a treadmill so that she/he can
walk forever. However, virtually all of these treadmills are relatively small and linear.
Thus, the space limitation is only resolved for one dimension. In short, none of these
restricted spaces enable truly normal walking behaviors like negotiating corners and
walking along nonlinear trajectories. However, none of these spatial limitations apply
to the CyberWalk platform. This then opens up a large range of possibilities for human
locomotion research. One straightforward opportunity is the possibility of replicating
the outdoor natural walking experiments described above (see Sect.
6.2.1
). An issue
with the natural walking study was the fact that turn angle and turn radius did not
change independently from each other, another was the need for the 9kilo backpack
to hold all of the recording equipment. By utilizing a carefully designed virtual
environment it becomes possible to control turn angles and radii. The backpack is
no longer necessary since most of the measurements can be made directly through
the optical tracking system, while other measurements (i.e., from the IMU) can be
implemented such that there is no additional load on the walker. Such a study would
effectively be an ideal marriage of the outdoor experiment [
97
] and the laboratory
study on head-trunk interactions [
98
].
More generally, the platform's optical tracking system is capable of full body
tracking which has enormous potential for extending studies of biomechanics and
dynamics (e.g., [
30
]) during real, unconstrained walking. Understanding uncon-
strained walking is not only of scientific value but can also advance computer vision
technologies for tracking and recognizing human locomotion behavior (e.g., [
1
]). The
platform's tracking capability can be extended to support gaze tracking by including
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