Biodynamic response of seated human body to roll vibration: Effect of armrest support

Human beings are exposed to whole-body vibration during daily life, which may cause discomfort or even sickness. Rotational vibration especially the roll vibration produces conspicuous discomfort. To promote the understanding of biodynamic characteristics of human body under roll vibration experimental research is carried out with eight subjects exposed to three levels of excitations. Different support conditions: rigid seat with and without armrests are applied and compared to investigate whether the armrest supports restrain or promote the response of human body to roll excitation. Apparent inertia is defined to represent the biodynamic characteristics of human body. A principal resonance at about 1 Hz and a secondary resonance at 2.5 Hz are detected in the roll apparent inertia. Armrest has little influence on the primary resonance frequency but decrease the first peak of apparent inertia, i.e., benefit the ride comfort. It is necessary that the height of armrests fits the stature of occupants so as to provide "effective" support and restrain occupants' response. A lumped parameter model of seated human considering the support condition is proposed. The modal properties of human body are obtained.