MODELLING OF THE BIODYNAMIC RESPONSES TO WHOLE-BODY VERTICAL EXCITATION

Modelling of the dynamic responses of humans to vibration is widely reported in the literature with more focus on responses in the direction of vibration excitation than responses in other directions. The aim of this paper is to develop a model that can predict the biodynamic responses in both the direction of excitation and in other directions during whole-body vertical excitation. The apparent mass was used to represent biodynamic responses in the direction of excitation and the fore-and-aft cross-axis apparent mass was used to represent the biodynamic response in the fore-and-aft direction. A series of lumped parameter linear models with rotational capabilities were developed to predict the vertical apparent mass and the fore-and-aft cross-axis apparent mass measured on the seat with vertical excitation. The final model suggested that three degrees-of-freedom (rotational, vertical and fore-and-aft) were needed to predict the vertical apparent mass and the fore-and-aft cross-axis apparent mass. The final model also suggested a fore-and-aft sliding motion (or possibly deformation of tissue in contact with the seat) of the human body on the seat when exposed to vertical excitation.