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Helicopter Flight Simulation Motion Platform Requirements(37)

时间:2011-11-12 12:15来源:蓝天飞行翻译 作者:admin
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For the high-gain and moderate phase-distortion case, configuration V3, all pilots noticed the necessity to change their control input technique. Two pilots noticed the unpredictability, or the “slipperiness,” of this config-uration. Only one downgraded the fidelity rating to medium. The objective performance did not change appreciably in the bob-up, but difficulty was perceived in repositioning downward. Although the ratings indicated the configuration was high fidelity, the comments and the performance did not agree. Thus, the V3 configuration should not be placed in the high-fidelity region.
Increasing the phase distortion further to the V4 configuration resulted in a perceived degradation in performance, and this is evident from the phase-plane data. The aggressiveness level was reduced, and the required compensation increased. Two of the three pilots noticed a phasing difference between the visual and the motion cues, yet with all of the above, they rated this configuration no worse than medium. However, one pilot thought that it was close to being objectionable. Considering the comments and the performance, it appears that the fidelity was closer to low than the rated medium, and thus no change is suggested.
Comparing these near-unity motion gain results with the only other set of high quality experimental data for heli-copters (ref. 24) shows similar trends. That experiment showed that for tracking a randomly moving target, while the open-loop crossover frequency remained nearly invariant with increases in motion-system phase distortion, the phase margin increased by 30° when going from a motion phase distortion of 108° to a phase distor-tion of 16°. For a phase distortion of 43°, which is similar to configuration V3, a phase margin degradation of 15° was measured. The comments and objective performance data from the present experiment, for these cases, indicated a similar trend in stability degradation, yet the subjective fidelity ratings for this task still rated the V4 configuration as medium fidelity.
In another experiment (ref. 60), for aircraft with poor longitudinal flying qualities in a landing task, it was observed that phase distortions higher than 90° caused “essentially uncontrolled touchdowns.” Thus, considering previous data and the lack of consistency in this experi-ment’s objective and subjective results for these config-urations, it seems appropriate to retain the hypothesized fidelity breakpoints suggested by Sinacori (ref. 44) for the near-unity gain configurations.
Returning to the low phase-distortion configuration with moderate gain, V5, pilot comments and objective perfor-mance generally indicated no degradation from the full-motion case. Only one pilot rated the fidelity as medium (owing to a slight vertical oscillation). From the consis-tency of these results, it appears that when the phase distortion is less than 30°, lowering of the gain required for high motion fidelity from 0.8 to 0.6 is appropriate.
 
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