This thesis presents modifications to classical washout algorithms to allow for large angular motion. This allows flight simulators with large angular motion envelopes to more effectively produce the motion cues for edge-of-envelope aircraft manoeuvres for pilot training. Classical washout is commonly used for flight simulation motion cues, but was originally designed for small simulator angular motion. With the development of the Atlas motion base allowing unbounded rotation about any axis, there is a need for washout algorithms which can exploit this extended angular motion envelope. Classical washout is implemented and the implementation is validated using numeric metrics, normalized Pearson correlation, integral of the error, and maximum error; and plots of the modelled vestibular response for the aircraft simulator pilot compared to previous reported results. This implementation is then used as a performance baseline for two proposed modifications to extend washout to larger angular motion envelopes. Large-angle washout uses quaternions and eliminates the small-angle approximations present in classical washout but continues to use highpass filters to impose restrictions on the simulator's angular motion during sustained angular velocity cues. Unrestricted angular washout removes the high-pass filters and allows for unbounded rotation about all axes. Using the numerical metrics and vestibular responses to assess the performance of the algorithms, for manoeuvres with small angular motion cues, the original classical washout algorithm designed for small angles performs best, and unrestricted angular washout has comparable performance. For manoeuvres with large angular motion cues, unbounded angular velocity washout performs best. Large-angle washout outperforms the small-angle washout for some large angular motion cues, but is outperformed by unrestricted angular washout, and performs badly for manoeuvres with small angular motion.
Washout algorithms are typically used in flight simulator motion control software to give the pilots flying the simulator the impression that they are experiencing an unlimited range of motion when the Gough-Stewart hexapod providing the motion cues has a comparably very small motion envelope. Since hexapods have generally been adopted by the motion simulator industry and the washout algorithms developed in the 1970s have performed extremely well at giving pilots a very high fidelity training experience despite the very small angular workspace of the motion platforms, research in the area generally came to a halt in the 1980s. We have succeeded in development of the Atlas motion platform which possesses an unbounded orientation workspace that is singularity free, hence we have the need to revisit washout algorithm development to take advantage of the unlimited orientation workspace. In this paper, after a brief review of existing approaches, we outline the development of our unlimited angular washout. Several benchmark cases are presented for two aircraft having very different flight characteristics: a Cessna 172 and a Columbia 400. Additionally, a quantitative comparison of small, large, and unlimited angular washout algorithm performance is reported.
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