Effects of occupant weight and sitting posture on vehicle seat structural dynamics

The characterisation of the occupied vehicle seat structural dynamics is still challenging owing to the complex and nonlinear dynamic behaviour of the human body. The human body has significant influences on the occupied vehicle seat structural dynamics. In this paper, the structural dynamics of the unoccupied seat, occupied seat in lean-on posture, and occupied seat in lean-off posture are investigated. The results of this investigation show that, in lean-on condition when the occupant weight increases, the lateral resonant frequencies of the seat decrease whereas both fore-aft resonant frequency and twisting resonant frequency increase. The structural resonant frequencies of the occupied seat in lean-off condition are considerably different from those in the corresponding lean-on condition. This indicates that the coupling of the occupant body and the seatback plays a major role on occupied seat structural dynamics and transmission of the vibration to the occupant body in frequencies where the seat has structural vibration modes.