Abstract

The perception of whole-body vibration and automotive driver/passenger comfort is strongly influenced by the static and dynamic properties of the seat. The analysis of comfort performance of the polyurethane foam (PUF) seats poses considerable challenges due to nonlinear properties of PUF and complex biodynamic response behavior of the human body. In this dissertation, the static and dynamic properties of three PUF seats are characterized in the laboratory under a wide range of preloads and excitation conditions. The measured data are analyzed to determine the stiffness and damping models of the seats as a function of the preload, and relative deflection and relative velocity of the cushion. The models thus derived are analyzed to study the vibration transmission performance of PUF seats loaded with a rigid mass under broadband as well as road-measured random excitation. Laboratory experiments are performed to evaluate vibration responses of the seat-rigid mass system and the data are used to examine the validity of the proposed models under the wide range of conditions considered. The analytical model of the seat-rigid mass system resulted in good agreements with the measured data in terms of acceleration transmissibility. A number of performance measures are formulated to assess the vibration isolation effectiveness of the seat. These included the true and frequency weighted rms acceleration, S.E.A.T. (Seat Effective Amplitude Transmissibility) values, and peak acceleration. A parametric study is carried out to study the influence of stiffness and damping gains, body-weight, frequency and relative deflection dependence of the PUF stiffness and damping on the vibration isolation effectiveness.