Biodynamic modeling of seated human subjects exposed to uncoupled vertical and fore-and-aft whole-body vibration

In this article, the biodynamic responses of Seated Human Subjects (SHS) exposed to uncoupled vertical and fore-and-aft Whole-Body Vibration (WBV) are modeled. The mathematical model can be used to obtain a better insight into the mechanisms and biodynamic behavior of the SHS system. The main limitation of some previous SHS models is that they were derived to satisfy a single biodynamic response function. Such an approach may provide a reasonable fit with the function data being considered but uncertain matches with the others. The model presented in this study is based on all three types of biodynamic response functions: Seat-To-Head Transmissibility (STHT), Driving-Point Mechanical Impedance (DPMI) and Apparent Mass (APM). The objective of this work is to match all three functions and to represent the biodynamic behavior of SHS in a more comprehensive way. Three sets of synthesized experimental data from published literature are selected as the target values for each of the three transfer functions. A curve fitting method is used in the parameter identification process which involves the solution of a multi variable optimization function comprising the root mean square errors between the computed values using the model and those target values measured experimentally. Finally, a numerical simulation of the frequency response of the model in terms of all three biodynamic functions has been carried out. The results show that an improved fit is achieved compared with the existing models.