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of the revised motion-fidelity criteria of Vertical
Experiment I, which are shown in figure 78. Since this
Low fidelity
0.0 0.2 0.4 0.6 0.8 1.0
0
20
40
Phase error (deg)
60
80
High fidelity
Medium
fidelity
Rotational gain
Low fidelity
0.0 0.2 0.4 0.6 0.8 1.0
0
20
40
Phase error (deg)
60
80
High
fidelity
Medium
fidelity
Translational gain
Figure 78. Revised motion fidelity criteria from Vertical
Experiment I.
experiment evaluated the effects of gain, and not the
effects of high-pass filter break frequency, the abscissas in
figure 78 can be combined as shown in figure 79. The
average motion-fidelity ratings for the tested configurations
are also shown on this combined specification.
In general, the combined specification matches well with
the data. The dividing line between High and Medium
fidelity would be at 2.5, and the dividing line between
Medium and Low fidelity would be 1.5. An instance that
does not match well is for the Klat = 0.4/Kroll = 0.2
configuration for Pilot 1. This configuration would be
predicted to be on the borderline of Low and Medium, and
this pilot rated the configuration High and Medium in his
two evaluations. The other two pilots rated it Low, which
matches prediction. Interestingly, Pilot 1 decreased his
rating to Low if additional lateral translational motion was
provided at the same roll gain. Because an increase in
lateral translational motion should not decrease the fidelity,
the ratings of Pilot 1 for this one point may be due to
a random effect, like the order of configurations that were
presented to him.
61
Figure 79. Proposed combined specification for roll/lateral
gains.
The second poor match is for the full-motion (Klat =
0.4/Kroll = 0.2) configuration. On average, the pilots rated
the fidelity of this configuration Medium. A possible
reason that Medium, instead of High, ratings were given
is that some of the undesired side-effects of providing
extremely large motion were noticed. An example of a
VMS artifact is the rack-and-pinion noise that is proportional
to lateral-track velocity. Pilots commented on the
noise, and since it represents a sensation noticeably
different from flight, a rating of Medium fidelity results.
Since the Klat = 0.8/Kroll = 0.6 configuration effectively
results in 48% of the lateral translational motion used in
the 1:1 case, artifacts such as the above are reduced
significantly. Another possible side-effect is the imperfect
high-frequency coordination between the roll and lateral
axes; for high-frequency tracking, using high gains can
reveal a noticeable, but not objectionable, sensation (i.e.,
the definition of Medium fidelity). Still, with these two
exceptions, the criterion in figure 79 correlates well with
the data.
63
8. Discussion of Overall Results
General Discussion
These experiments showed the powerful effect that
platform motion has on pilot-vehicle performance and on
pilot opinion in flight simulation. Often, the quantitative
measures have supported the pilot’s subjective measures,
which adds confidence to the results. In addition,
frequency-response analyses offer an explanation of how
the characteristics of the motion filter affect closed-loop
performance.
The powerful effect of motion was shown even when the
pilot was creating his own motion, which was the case in
all of the tasks except the disturbance-rejection task
discussed in section 5. This result conflicts with the views
of Hunter et al. (ref. 14) and Puig et al. (ref. 15). The
difference between these two views is almost certainly a
result of differences in vehicle dynamics. At low speed,
fixed-wing aircraft on stabilized paths do not require as
much compensation from a pilot as do helicopters. In
addition, the tasks that helicopters perform often require
the pilot to control all six degrees of freedom of the
vehicle simultaneously. Improved fidelity of external cues,
such as motion cues, aid in the effective pilot control of
the vehicle. Thus, motion requirements cannot be defined
by task alone. Both the task and the vehicle must be
considered in concert.
This report has illustrated the performance and opinion
differences that arise when simulator motion is provided,
but it has not shown if there is any training benefit to the
use of motion. It is possible that training in a more
difficult task environment (no motion) may actually
shorten or improve training. For instance, learning to
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Helicopter Flight Simulation Motion Platform Requirements(40)
