Vibration isolation in neonatal transport by using a quasi-zero-stiffness isolator

New-born infants are likely to suffer excessive vibration during neonatal transport, but there is no effective method to attenuate the transmission of vibration from the ambulance floor to an infant. This would be particularly detrimental to premature or sick new-born babies. In this paper, a quasi-zero-stiffness (QZS) vibration isolation method is proposed to improve the comfort of the infant in an incubator. The infant compartment is supported by quasi-zero-stiffness isolators, which are realized each by combining a pair of mutually repelling permanent magnets in parallel connection with a coil spring, and their parameters are obtained by design optimization to maximize the displacement range with smaller stiffness than that of the coil spring. A lumped-mass model of the transport incubator is developed, and the vibration isolation performance is estimated in terms of displacement and acceleration transmissibility. Numerical results reveal that a comparatively heavy damping is needed to completely avoid the jump phenomenon inherent in polynomial nonlinearity and suppress resonance, and thus achieve smooth and effective vibration attenuation starting from an ultra-low frequency. Under a random disturbance, magnification of vibration is observed in the original transport incubator, but notable attenuations of root mean square (RMS) acceleration and displacement in the modified one, which indicates that the proposed quasi-zero-stiffness isolator should be a good solution to eliminate vibration-induced injuries in neonatal transport.