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balance a short inverted pendulum can train a person to
balance a long inverted pendulum easily. However, if lack
of motion causes a bad habit to be learned, then that
would certainly argue against training without motion.
The effectiveness of training without motion would
require a careful transfer-of-training study.
Among the motion configurations tested, it was the
translational motion that always had a strong effect. Yaw
rotational motion was shown to be a redundant cue, and
less roll motion was more acceptable (when comparing
percent of full motion) than less lateral translational
motion. Requiring less motion in the rotational axes is
still consistent with the revised set of the Sinacori criteria
that were suggested in this report.
A question arises as to why only one of the three
rotational cues is redundant. That is, why is yaw rotational
motion redundant, but pitch and roll motion useful?
A possibility is that the pitch and roll rotational cues (as
sensed by the inner ear) are no more important than the
yaw rotational cue, yet their usefulness arises from the
additional cues concomitant with pitch and roll motion.
These additional cues have two sources.
First, pitch and roll motion cues interact with the gravity
vector, as discussed in section 7. Very few simulators can
remove the specific force cue that arises from either pitch
or roll attitude. As such, evaluating the effect of the
angular cue only is challenging; it has only been investigated
by Jex et al. (ref. 41) in which subjects rolled while
lying on their backs (thus the gravity vector did not
change relative orientation during an orientation).
Although that study showed an effect of roll, this could be
due to another factor (in addition, it might be argued that
compelling roll visual cues were not present in that study,
as only a horizon line was present).
The other factor is the tangential acceleration that results
from the moment arm between the roll center of rotation
and the motion sensors on a human. It is not possible to
eliminate the effect of these tangential accelerations
completely, for the human motion sensors are in different
locations (inner ear, neck, buttocks, limbs). Some
experiments have isolated the head by fixing it in an
apparatus and subsequently performing reorientations
about that axis, but those were not piloted experiments.
Thus, when pitching and rolling, isolating the angular cue
from the translational cue is difficult if not impossible. It
is only in yaw that many of these cross-coupling effects
into the translational axes are lessened (but perhaps not
removed completely, as discussed in sec. 3). Thus, the
above reasons may explain why the requirements on the
yaw axis are different from pitch and roll.
Although the longitudinal axis was not examined in these
studies, no reason is offered as to why the requirements in
that axis might be different from those in either vertical or
lateral translation.
64
Proposed Fidelity Criteria versus Results of
Previous Research
Since a cornerstone of the results presented herein was the
modification and validation of the fidelity criteria in
figure 78, placing those criteria in the context of other
work is important. The results of previous work are
discussed in section 1, and figure 80 correlates the previous
work with the new criteria suggested here. In
figure 80, the points tested and found to have at least
adequate fidelity are shown. The word “adequate” is chosen
in an effort to make a consistent comparison with the
earlier work. Much of the earlier work attempts to define a
boundary between adequate and inadequate rather than
breaking down adequate into three categories such as High,
Medium, and Low fidelity. However, it is appropriate that
the user should strive to stay away from Low fidelity,
which would certainly be termed as inadequate, for the
motion sensations are objectionable. Thus, in comparing
the previous work with the proposed criteria, an
inconsistency would be present if previous work stated
that an “adequate” motion system setup was in the
proposed Low fidelity region.
In the rotational axes, the criteria apply only to pitch and
roll; yaw was found to be redundant. Only the work of
Bergeron (ref. 38) evaluated a range of yaw configurations,
which was discussed earlier. The only inconsistency
between the previous work and the criteria suggested is the
work by Shirachi and Shirley (ref. 42). Their experiment
did not vary motion-filter natural frequency, which
provided 62.5° of phase distortion at 1 rad/sec, which is
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Helicopter Flight Simulation Motion Platform Requirements(41)
