Effects of human body weight on the vehicle seat structural dynamics

The characterization of the occupied vehicle seat is still challenging. This is due to the complex and non-linear dynamic behaviour of the human body when exposed to vibration excitation. The structural dynamics of seat system changes when the seat is occupied by volunteers with different weights and different posture. Adding the occupant to the seat is reported to change the seat structural resonant frequencies. However, it is not clear how different occupants' weights and seat posture may change the seat vibration responses. The results of this investigation show that when the seat occupant weight increases, the lateral resonant frequencies of the seat decrease while fore-aft resonant frequency increases. Nevertheless, the results show that the seat torsion resonant frequency was not affected significantly by the occupant weight. Comparison of the lean-on and lean-off seating posture shows that the occupied seat in lean-off posture seat do not show significant structural resonant frequency changes from its corresponding unoccupied seat. This indicates that the interaction of the human body trunk and the seatback is relatively significant for the transmission of the vibration to the human body.