Modelling of seated human body exposed to combined vertical, lateral and roll vibrations

Abstract Existing models of the seated human body are mostly two-dimensional and developed in the mid-sagittal plane exposed to in-plane excitation, which has limitation when the human body is exposed to vibrations in the mid-coronal plane. Based on the characteristics of ride dynamics of rail vehicles such as high-speed trains and on experimental biodynamic responses, a multi-body dynamic model of the seated human body was developed. The model consists of abdomen, pelvis, thighs, upper torso (including shoulders, thorax, and arms), head and neck exposed to combined lateral, vertical and roll vibrations. While some of the model parameters were derived from literature available, others were determined by a procedure of model calibration with a combined genetic algorithm and a minimization algorithm for constrained nonlinear multivariable problem. For calibration, measured lateral and vertical apparent masses at both the seat pan and backrest in the frequency range 0.5–20 Hz were used. The model can be used for the analysis of ride vibration and comfort of passengers of rail vehicles with different weights and heights exposed to multiple excitations in lateral, vertical and roll directions. The adopted methodology may also be applicable to similar analyses of other types of vehicles and seats with varied inclination angles of backrest. A modal analysis with the calibrated model revealed three vibration modes of the seated human body, which were correlated with the resonances observed in the measured apparent masses. The first mode was found to be associated with the lateral and roll motions of the upper body, the second with lateral motion of the lower body in addition to these upper body motions, and the third mode shape was dominated by the vertical motion of the whole body.