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0.9
0.2 1.0
0.5
1.0
0.9
0.7
0.2
0.7
0.5
0.3
0.2 0.3
0.5
0.4
0.9
0.0
0.0 K
w
Figure 56.Target-following pilot-vehicle open-loop crossover frequencies.
(ref. 54), for these data, the differences among the configurations
were not significant at the 5% level. In addition,
no coherent trend was present among the motion-filter
variations. This result agrees with, and extends, the results
of Bray (ref. 24), which indicated an invariance in targetfollowing
open-loop crossover frequency for motion filter
natural frequencies between 0.2 and 1.25 rad/sec with K =
1 for all configurations. The results from the present
experiment indicate that this invariance across natural
frequency variations also holds for motion-gain changes.
Thus, it appears that the initial quickness with which the
pilot closes the target-tracking loop does not depend on
the motion cue. That result is intuitive; it might be
expected that the speed with which this loop is closed
would be based on a pilot’s mental model of the speed
with which the loop should be closed. The pilot initiates
and generates his own motion in this loop.
Figure 57 shows the target-following loop phase margins
for all configurations. Unlike the target-following crossover
results, statistical differences are present in the phase
margins, although the range of the means is only 10°. The
largest phase margin occurred with the full-motion
condition (V1), and phase margin was progressively lost
as K was reduced and wm was increased. Using the
Newman-Keuls method (ref. 62) to determine which
means are statistically different from each other at the 5%
level, the results indicate that configurations V1 and V3
were different from V4 and from V6–V10, and that
configurations V2 and V5 were different from V8.
V1 V2 V3 V4 V5 V6 V7 V8 V9 V10
0
10
20
30
40
50
Configuration
Phase margins, mean and rms, deg
1.0
0.0 0.9
0.2
1.0
0.5
1.0
0.9
0.7
0.2
0.7
0.5 0.3
0.2 0.3
0.5
0.4
0.9
0.0
0.0
K
w
Figure 57. Target-following pilot-vehicle open-loop phase margins.
45
These results are partially consistent with those of Bray
(ref. 24), which indicated that target-tracking phase margin
degraded as wm was increased from 0.2 to 1.25 rad/sec at a
unity gain (K = 1). However, Bray’s results exhibited
larger variations in the measured phase margins, including
an almost 20° variation between wm = 0.2 and 0.5 rad/sec.
Only a slight difference was measured in this experiment
between the nearly equivalent V1 and V2 motion
configurations.
These phase-margin target-following results suggest that
the resulting damping of the error to a nulled steady-state
value is affected by motion variations. This result is
consistent with the results in section 4. That is, as the
quality of the motion improved in that purely targetfollowing
task; the principal effect on performance was in
damping (see figs. 40–49).
It was also suggested in section 4 that the high-fidelity
portion of the Sinacori criterion should include configuration
V5. The performance results shown here for target
following are consistent with that suggestion.
Disturbance Rejection. Pilot-vehicle open-loop
crossover frequencies for the disturbance-rejection loop are
shown in figure 58. The crossover magnitudes appear to
be roughly ordered by phase distortion level, that is, by
successive increases in wm. The statistical results reveal
that at the 5% level, configurations V1, V2, and V7 all
had higher crossover frequencies than the fixed-base case
V10. Again, these results are consistent with the
configurations tested by Bray (ref. 24), and they extend
those results by suggesting that the open-loop crossover
appears to be affected by changes in wm at all levels of
motion-filter steady-state gain K.
Figure 59 shows the disturbance-rejection loop phase
margins. Here the configurations are ordered by progressive
reductions in K. Statistically, configuration V3 was
better than any of the other cases, and configurations V1
and V4 were better than V10. Bray showed, for K = 1, that
the low and high phase distortion cases have roughly the
same phase margin, with perhaps a slight peaking at
moderate amounts of phase distortion. Here, more relative
peaking in phase margin was observed for the V3 case
than was found by Bray. The crossover frequency for
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Helicopter Flight Simulation Motion Platform Requirements(31)
