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Results
The results of Vertical Experiment I consist of objective performance data and subjective fidelity ratings. Relevant pilot comments will be added in the discussion of these results.
Objective Performance Data
Again, compelling performance differences are shown between full motion and no motion in figure 39 (configurations V1 and V10, respectively). For the configuration V1 case, well damped, accurate bob-ups were achieved with the vertical velocity remaining within 10 ft/sec; the vertical acceleration remained within 0.5 g, and the collective stayed within 1.5 in. A drastic difference is evident in the no-motion case (V10). Initially, the pilot overshot the 85-ft desired altitude and then returned to the starting point as he responded to the unfamiliar cues. Since the acceleration feedback cue was the only cue that changed from the full- to the no-motion case, part of the pilot’s collective input must have been a result of that cue. With the acceleration cue removed in the V10 configuration, the pilot had to adjust his compensation based on the new set of cues. With time in the motionless configuration, the performance improved, but even the final repositioning took longer in the fixed-base case than in the full-motion case. These differences have obvious training implications, for the pilot must develop different mental compensation between the two cases. No data were taken when returning to the full-motion case for recalibra-tion, but pilots commented that relearning the full-motion configuration was easy and natural.
Figures 40 through 49 show phase-plane portraits for each motion configuration. Each portrait shows three runs, one for each pilot, using his best performance run if an evalu-ation was repeated. Both the bob-up and bob-down are shown. These plots show how the motion changes affected the pilot’s ability to capture the upper desired point smoothly. Ideally, these plots should be well-damped and approximately oval.
Figure 40 indicates that some overshoots were present for the full-motion condition, but overall the trajectories were well damped and smooth. There was reasonably precise control about the 85-ft altitude point, with one instance of a pilot not arresting the vertical velocity soon enough, which caused a position overshoot. Little change in performance, or perhaps a slight improvement, is noted for the slight motion changes of configuration V2 in figure 41.
The high-gain, moderate phase-distortion case of configuration V3 in figure 42 still produces well-damped trajectories on ascents. The acceleration cues for this configuration lead the math model by 90° at 0.52 rad/sec. If the motion between the ascents and descents were sinu-soidal, the frequency of the maneuver would be approxi-mately 2 rad/sec. This value is approximated by letting
h = 80 + 5sin ωt (13)
˙
h = 5ω cos ωt (14) ˙
10ft /sec .ω = 2 rad / sec (15)
hmax =
For the initial phase of the maneuver, therefore, the motion cues would be accurate, but the subsequent stabilization at a particular altitude would produce some miscues, for lower frequency content would be present. Pilots seemed to have more difficulty in returning to the starting point than in the first two configurations; however, this repositioning was not officially part of the evaluations. For the high-gain and high-phase-distortion case of configuration V4 in figure 43, the overshoots were more prominent, and the overall control was much less precise.
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本文链接地址：Helicopter Flight Simulation Motion Platform Requirements(34)
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