Structural dynamic characterization of a vehicle seat coupled with human occupant

Predicting the responses of the combined human body-seat structure to vibration excitation is still a challenging task. This is mainly due to the complex dynamics behaviour of the seated human body in response to vibration. It is however essential to characterize and predict the critical frequencies and the corresponding vibration patterns of the seat when it is coupled with a human occupant. This study provides important knowledge to predict the structural resonant frequencies and corresponding vibration mode shapes of the vehicle seat coupled with occupant from the seat alone or seat bare-frame (seat without foam cushion). An experiment is designed to measure the frequency responses, resonant frequencies, and corresponding mode shapes of the three different selected vehicle seats when mounted on the test rig. Six volunteers have participated in the experiments. The experiment data for each of the seats were collected for the seat bare-frames, seat alone (seat with foam cushion), and seat with human occupant. The results indicate that the vehicle seat bare-frame, seat alone, and seat with occupant have similar main seatback lateral, seatback fore-aft, and seat twisting structural resonant frequencies below 80 Hz. The coupling of the seated human body with the seat shows that the human occupant is not adding any new structural resonant frequency or mode shape to the seat below 80 Hz. It is therefore possible to characterize and predict the key vibration attributes such as occupied seat structural resonant frequencies and mode shapes from their corresponding unoccupied seat or bare frame characteristics. This alleviates the need for complex modelling or detailed analysis of the human body structure itself.