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5.
Vertical motion cues affected altitude estimation. Pilots, when asked to double or halve their altitude, had their performance significantly affected by vertical platform motion. With vertical motion, pilots more accurately doubled and halved their altitude. Until now, it was generally accepted that steady-state altitude estimation was derived from visual cues only. A hypothesis is that the pilot estimates vehicle state using all the available sensory inputs. As a part of this, some significant weighting is applied to acceleration cues that provide a component of the pilot’s position estimate.
6.
A specification for roll-lateral motion requirements was developed. For a side-step task that exactly reproduced motion and visual cues, significant performance and opinion differences resulted as motion was removed. A combination of translational and rotational gain specifications provided a good prediction of motion-fidelity ratings.
Recommendations for Future Work
1. Two additional degrees of freedom, pitch and surge, should be examined. The results for these two coupled axes are expected to be similar to those of the coupled roll and lateral axes.
2.
The specification demarcations between high, medium, and low fidelity were determined based on the granularity of the points tested. Further efforts are needed to determine the curves that divide the fidelity regions more precisely.
3.
Controlled experiments should be performed on several representative hexapod platforms to quantify the performance benefits of allowing increased motion in the other axes when turning the yaw rotational displacement off.
4.
Continued attempts should be made to model the pilot-vehicle system in the simulator environment. Several unusual results, such as the performance degradation with the addition of yaw rotational motion and the improved estimation of height with the addition of vertical motion have been shown here. Future models need to account for these findings.
5.
Does learning to fly a helicopter on a substandard or suboptimal motion platform increase total training costs, or does it pose a safety hazard? To answer these questions, a careful transfer-of-training study needs to be performed.
Appendix A—Human Motion Sensing Characteristics
Models of how the semicircular canals and the central nervous system combine in the perception of angular movement have been treated in several research summaries (refs. 28–31). Subtle differences exist among the model structures reviewed. Significant differences, sometimes by several orders of magnitude, exist among measured numerical values in the respective structures. This appendix discusses factors that are important in pilot-vehicle dynamics modeling and in understanding human perception of motion in flight simulation.
A model for angular velocity sensation is shown in figure A1. The semicircular canals are roughly orthogonal to each other, and each behaves like an overdamped torsional pendulum (ref. 32). The output of each block is the deflection of the canal’s cupula, and when it reaches a threshold deflection, a sensation develops. Van Egmond et al. (ref. 32) determined the time constants for yaw to be
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