Study on the vertical vibration of an occupant - seat cushion system

Dynamic interaction between a human body and the seat cushion was addressed, aiming at seat design for better NVH performance of a passenger vehicle. Referring to DIN EN ISO 3386-1 and previously researches, static and dynamic tests were conducted on polyurethane foams typically used as vehicle seat cushions. A one-dimensional stress strain relation was derived based on the measured data, in which the nonlinear elastic behavior of the foam material is regarded as piecewise linear in terms of the static strain while the viscoelastic property is described using a fractional derivative. A model was then established with some simplification to reflect the interaction in the vertical direction between a foam cushion and a seated occupant, where the seated human body was depicted by a lumped parameter model. Apparent mass of the system was calculated using the model, which were validated by experiments with or without seat cushion. The influence of the foam cushion is thus demonstrated on the vertical vibration of the occupant, which will be helpful to vehicle seat design.