A study on biodynamic models of seated human subjects exposed to vertical vibration

Humans are most sensitive to whole body vibration under low-frequency excitation in seated posture. As a result, biodynamics of seated human subjects has been a topic of interest over the years, and a number of mathematical models have been established. While much research has been performed on building up specific biodynamic models based on certain experimental data under prescribed testing conditions, a thorough investigation of mathematical human models in seated posture has not yet received the same level of attention. In this paper, a complete study on lumped-parameter models for seated human subjects without backrest support under vertical vibration excitation has been carried out. As part of the study, all models have been analyzed systematically, and validated by the synthesis of various experimental data from published literature. Based on the analytical study and experimental validation, the four-degree-of-freedom (DOF) model developed by Wan, Y. and Schimmels, J.M. [1995. A simple model that captures the essential dynamics of a seated human exposed to whole body vibration. Advances in Bioengineering, ASME, BED 31 333–334] is found to be best fitted to the existing test results, and is recommended for the study of biodynamic responses of seated human subjects under vertical whole body vibration. In addition, for the cases such as the female pregnant, more mass segments might be needed in the analysis. The six-DOF linear model from the modification of nonlinear model established by Muksian, R. and Nash, C.D. [1974. A model for the response of seated human to sinusoidal displacements of the seat, Journal of Biomechanics 7, 209–215] will be suggested.