Dynamic Characteristics of Infants Riding on Stroller

When stroller rides over protrusions or irregularities, vibration is transmitted from the lower limb to the upper limb of the infant through the tire-frame-cushion.

In order to reduce the load on the infant, the challenge is to reduce the vibration at each part of the infant.

To design an equipment for the vibration reduction, it is important to understand the vibration characteristics of infants.

The purpose of this study is to clarify the vibration characteristics of infants.

Transient and frequency response characteristics of the infant - stroller system were investigated by riding over protrusions and irregularities, respectively.

In the transient response riding over the protrusion on both wheels, the vibration of the head and the chest is a mixture of the primary vibration mode and the secondary vibration mode.

In the transient response riding over the protrusion on one wheel,

the primary vibration mode becomes prominent when the vibration transmitted to the stroller seat is small, and the secondary vibration mode becomes prominent when the vibration transmitted to the stroller seat is large.

In both RMS values of the acceleration riding over the protrusion on both wheels and one wheel, it is considered that the value of the head where the moment works more easily is large in the longitudinal direction because the distance from the vibration source is long. The value of the chest, which is more susceptible to vibration, is large in the vertical direction because the distance from the vibration source is close. It is also clear that the horizontal direction is smaller than the longitudinal direction and the vertical direction.

In addition, there is no difference in the RMS values of the acceleration in the horizontal direction riding over the protrusion on both wheels and one wheel. On the other hand, acceleration ratio by one wheel is larger than that by both wheels.

In the acceleration ratio in the horizontal direction, the value on the side over the protrusion tended to be small when the stroller rode over the protrusion smoothly, but the value on the side over the protrusion tended to be large when the stroller stumbled over the protrusion. From the result, it was clear effects of vibrations getting over the protrusion on the acceleration ratio in the horizontal direction.

In the frequency response, there are some resonance frequencies between 1 and 6 Hz. Vibrations over 8 Hz have small effects on the infants, because acceleration ratio are low values under 1.