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Rotation sequences - Standardized CS

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  • Rotation sequences - Standardized CS


    I do not have a recommendation for a standardized coordinates
    systems (CS). I do however have a concern over some recommendations of
    Euler/Bryant sequences (i.e. the six sequences of [X][Y][Z], [X][Z][Y],
    etc.) that appear to be finding their way into the standardization of CS.
    If there is a concensus for a standard CS, fine, but I strongly disagree
    with a standard for the sequence of rotations.
    When rotation occurs about an axis of the defined CS, there are
    negligible differences between the six sequences. Thus, there is not a
    problem. However, as the axis of rotation deviates from the axes of the
    CS, the differences between the sequences can easily reach factors of 2
    (100% difference) or greater. Which sequence is best? NONE. When the
    rotations are highly coupled (i.e. the axis of rotation has significant
    components in each direction), each of the sequences gives rotations that
    are non-intuitive. In these cases, I believe that the helical axis of
    motion is the best choice for describing complex coupled motions.
    In summary, if there is a concensus to standarized CS, fine (my
    vote is one is not needed), but do not attempt to include a standard
    sequence for calulating the rotations in that standard.

    Trey Crisco, Ph.D.