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Helicopter Flight Simulation Motion Platform Requirements(42)

时间:2011-11-12 12:15来源:蓝天飞行翻译 作者:admin
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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 cross-over 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 ω m 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.
Phase margins, mean and rms, deg
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Configuration
These results are partially consistent with those of Bray (ref. 24), which indicated that target-tracking phase margin degraded as ω m 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 ω m = 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 target-following 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 config-uration 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 ω m. 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
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Crossover freq., mean and rms, rad/sec
appears to be affected by changes in ω m 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 progres-sive 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 V3 was reduced, which alone might contribute to an increased phase margin; however, V4 had a low crossover frequency, but not an accompanying phase-margin peak. With the unknown details of the pilot feedbacks, the V3 configuration must be coupling in with the vehicle dynamics in a manner different from that in the other configurations.
 
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