This paper deals with the determination of the seat sponge parameters by using the estimated nine degree-of-freedom (DOF) biodynamic model. The suggested nine DOF model has multiple outputs that include the major axes for evaluating the ride quality in vehicles such as z-axis of the floor, hip, and x-axis of the back, in addition to the z-axis of the head for describing the whole-body vibration. It is intended to resemble the sitting posture with backrest support. Three experiments were executed to validate the proposed models. The first one was to measure the acceleration of the floor and hip in z-axis, the back in x-axis, and the head in z-axis under exciter. The second one was the measurement of joint positions, and contact points between the human body and the seat. The third one was the dropping test to measure the seat and back cushion. The biodynamic model parameters were obtained by matching the simulated to the experimental transmissibilities at the hip, back, and head. From this estimated model, the optimal seat parameters are determined to minimise the overall ride value at the floor, hip, and back on three kinds of roads (highway, Korean national road, and unpaved road), with the constraint that the stiffness of sponge has a roughly linear relation with the damping. Concerning the optimal seat sponge characteristics it is found that the lower stiffness and damping transmits the lower vibration to the human body.
Abstract