Motion sickness with fully roll-compensated lateral oscillation: effect of oscillation frequency.

BACKGROUND

During lateral acceleration, the addition of an appropriate roll motion can improve comfort, but some combinations of lateral and roll motion increase motion sickness.

OBJECTIVES

To determine how motion sickness caused by lateral oscillation fully compensated by roll oscillation (so subjects feel no lateral acceleration) depends on the frequency of oscillation and compare sickness with that caused by uncompensated lateral oscillation.

METHOD: A total of 160 subjects (8 groups of 20) were exposed for 30 min to fully roll-compensated sinusoidal lateral oscillation at one of 8 frequencies (0.05, 0.08, 0.125, 0.16, 0.20, 0.315, 0.5, 0.8 Hz). A further 60 subjects (3 groups of 20) were exposed to lateral oscillation (at 0.315, 0.5, or 0.8 Hz) to allow comparison of sickness with that caused by uncompensated lateral oscillation at frequencies not previously studied. Subjects rated symptoms at 1-min intervals.

RESULTS

With fully roll-compensated lateral oscillation, illness ratings tended to increase with increasing frequency of oscillation from 0.05 to 0.2 Hz (with peak lateral velocity, +/- 1.0 m x s(-1)) and tended to decrease from 0.315 to 0.8 Hz (with peak lateral jerk, +/- 1.96 m x s(-3)). Roll compensation significantly reduced the duration before subjects developed nausea.

CONCLUSIONS

Motion sickness is increased by roll oscillation used to compensate fully for low-frequency lateral oscillation. In general, when roll oscillation is combined with low-frequency lateral oscillation, motion sickness cannot be predicted from either the roll oscillation or the lateral oscillation alone. The dependence of motion sickness on the frequency of oscillation is broadly similar for pure lateral oscillation and 100% roll-compensated lateral oscillation.