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Helicopter Flight Simulation Motion Platform Requirements(10)

时间:2011-11-12 12:15来源:蓝天飞行翻译 作者:admin
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Remnant

Simulator
stick

Pilot
Task
force
demands Simulator visual, motion, and stick cues


Figure 2. Top-level pilot model.
The sensation block in figure 2 is often used as the starting point when motion requirements are hypothesized, and a large database exists on human motion-sensing characteristics (refs. 28–36). The details of the human motion sensing systems are given in appendix A, but four key points are made here. First, the bandwidth of the total human motion sensory system encompasses the typical pilot-vehicle range of frequencies (0.1–10 rad/sec). Second, for the experiments that are subsequently described, the thresholds of human motion sensors were exceeded; however, the literature acknowledges that motion-sensing thresholds differ among individuals and that they depend on whether the subject is active or passive during the motion stimulus (ref. 36). Third, previous incorporation of the motion dynamics and thresholds into models of a pilot-vehicle system has not resulted in an improved ability to model pilot-vehicle behavior (ref. 35). Finally, previous efforts to generate an integrated motion cueing model have concluded that additional experiments need to be conducted before that goal can be accomplished (ref. 31).
Once the cues are sensed, the perception block of figure 2 comes next. At this point, an integrated perceptual process likely occurs, but how it is accomplished is not known exactly. One has to know how all of the external cues (visual, kinesthetic, and tactile) are summed to develop the pilot’s perception of motion. Unfortunately, little is known about how these cues affect motion perception, and further careful experiments are required to explore the perceptual interactions that occur among these cues.
After the pilot has developed an estimate of the vehicle state from the output of the perception block, compensa-tion is then applied to this state vector. Fundamentally, it is known that the pilot applies compensation necessary to have “integrator-like” or “K/s-like” characteristics in the crossover region of the pilot-vehicle open-loop combina-tion (ref. 37). To do this, a pilot will typically provide up to 1 sec of lead before his estimate of a task workload is degraded.
Application of the above concepts is presented in appendix B, which gives details of a structural pilot model for the vertical axis experiment described in section 4. It is shown that the model captures the general closed-loop performance trends. However, it underpredicts the magnitude of these trends to the point that it suggests no fidelity differences should exist when, in fact, they do exist. In addition, the model is incomplete, for it does not account for the gain on motion platform acceleration.
To summarize, a credible analytical model does not yet exist for flight simulation. More experimental data are needed to develop and refine the model further. The experi-ments that have been performed to date are discussed next.
 
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