Abstract
This paper presents a proposal for a restraint method to limit ride discomfort that occurs during rotational transport by a stretcher. Although increased angular velocity of the stretcher degrades the ride quality of the transported subject, the transient response between the angular velocity and the ride discomfort is unknown. Therefore, a mathematical model to estimate the ride discomfort is identified using least-squares method. Moreover, the ideal rotation method to reduce the ride discomfort is estimated using computer simulation and is confirmed experimentally. To develop the model, six healthy volunteers rode on the stretcher in a supine position to evaluate the ride discomfort. The method of continuous judgment by category every 1 s is applied while exposed to the rotational transport with several angular velocities and durations. The derived model is analyzed numerically to propose an ideal rotation method to minimize ride discomfort after examination of all possible angles of rotation of 0-90 deg within 4 s. The ideal rotation was obtained such that the stretcher proceeds to angles of 44 deg, 53 deg, 84 deg, and 90 deg every 1 s. To confirm the effect of the ideal rotation on the reduction of ride discomfort, 10 healthy volunteers evaluated the ride discomfort of normal rotation with constant angular velocity and the ideal rotation. The experimentally obtained results show that the ideal rotation provides more comfortable transportation than conventional rotation does : the maximum value and cumulative value of ride discomfort are considerably lower by application of the ideal rotation.
