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Although definitive answers regarding necessary motion requirements do not exist, regulators still suggest which motion degrees of freedom may be useful. These sugges-tions depend on the level of simulator sophistication desired by the user. For instance, the FAA specifies two levels of motion sophistication for helicopter flight simulators: full six-degrees-of-freedom motion, and three-degrees-of-freedom motion (ref. 5). For the latter, the nominal three degrees of freedom are pitch, roll, and vertical. If degrees of freedom different from these are selected by a user, they must be qualified by the FAA on a case-by-case basis. Although the selection of the pitch, roll, and vertical degrees of freedom is reasonable, evidence to support the selection of these axes or any set of axes is lacking. Even though existing motion criteria are incomplete, however, considerable research has been performed. To divide and conquer the problem, the six degrees of freedom are often broken into two categories: rotational motion and translational motion. But even at this high level, differences in opinion exist on the relative cueing impor-tance of these two categories. For example Stapleford et al. (ref. 26) state, for tracking, “Translational motion cues appear to be generally less important than rotational ones, although linear motion can be significant in special situations.” Young states “For most applications, simu-lation of vehicle angular motions is more important than translational simulation” (ref. 18). In contrast, the concluding remarks of Bray (ref. 27) state, “For large aircraft, due to size and to the basic nature of their maneuvering dynamics, the cockpit lateral translational acceleration cues appear to be much more important than the roll acceleration cues. There was the indication that this observation might be extended to the generalization that, in each plane of motion, the linear cues are much more valuable than the rotational cues.” Reasons for these differences of opinion at a high level are unclear and point to the need for additional research. But before the appropriate directions for the additional research can be determined, a careful review of past work is warranted. Those analytical and experimental efforts that have addressed motion requirements are discussed below. Analytical Motion Research. Many decisions are made during both the design and development of a particular simulation. All of the components shown in figure 1 must be selected, and their characteristics must be specified. If an analytical model was available that accounted for the fidelity effects of these components, then one could inexpensively make performance trade-offs to optimize both the cost and utility of a simulator system. So, a good analytical model would have great use. Although the dynamics of the non-piloted components of figure 1 are straightforward, the difficulty facing the modeler is the pilot block. Pilots are often adaptive, nonlinear, and inconsistent, and modeling their input/ output characteristics is a challenge. A possible break-down of the key processes carried out by a pilot is shown in figure 2. These key processes are sensation, perception, and compensation. The general characteristics of these processes are discussed next, because knowledge of them is relevant to the experimental designs presented in later sections. 直升机网 www.helicopter.cn 直升机翻译 www.aviation.cn 本文链接地址：Helicopter Flight Simulation Motion Platform Requirements(9) |
