When a stroller with an infant ride over protrusions or irregularities, vibrations are transmitted from the infant’s lower limb to the upper limb through the tire-frame-cushion. To reduce the load on the infant, the challenge is to reduce the vibration at each part of the infant’s body. To design an equipment for reducing such vibration, it is important to understand the vibration characteristics of infants. Therefore, the purpose of this study was 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 obtained by both wheels riding over the protrusion, the vibration of the head and chest is a mixture of the primary secondary vibration modes. In the transient response obtained with one wheel riding over the protrusion, 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. The frequency response shows some resonance frequencies between 1 Hz and 6 Hz. Vibrations over 8 Hz have small effects on the infants because the acceleration ratio is low at values below 1.