Three Dimensional Modeling of Supine Human and Transport System Under Whole Body Vibration

Abstract

The development of predictive computer human models in wholebody vibration has shown some success in predicting simple types of motion, mostly for seated positions and in the uniaxial vertical direction. The literature revealed only a handful of papers that tackled supine human modeling in response to vertical vibration. The objective of this work is to develop a predictive, multibody, threedimensional human model to simulate the supine human and underlying transport system in response to multidirectional wholebody vibration. A threedimensional dynamic model of a supine human and its underlying transport system is presented in this work to predict supinehuman biodynamic response under threedimensional input random wholebody vibration. The proposed supinehuman model consists of three interconnected segments representing the head, torsoarms, and pelvislegs. The segments are connected via rotational and translational joints that have springdamper components simulating the threedimensional muscles and tissuelike connecting elements in the three x, y, and z directions. Two types of transport systems are considered in this work, a rigid support and a long spinal board attached to a standard military litter. The contact surfaces between the supine human and the underlying transport system are modeled using springdamper components. Eight healthy supine human subjects were tested under combinedaxis vibration files with a magnitude of 0.5 m/s2 (rms) and a frequency content of 0.5–16 Hz. The data from seven subjects were used in parameter identification for the dynamic model using optimization schemes in the frequency domain that minimize the differences between the magnitude and phase of the predicted and experimental transmissibility. The predicted accelerations in the time and frequency domains were comparable to those gathered from experiments under different anthropometric, input vibration, and transport conditions under investigation. Based on the results, the proposed dynamic model has the potential to be used to provide motion data to drive a detailed finite element model of a supine human for further investigation of muscle forces and joint dynamics. The predicted kinematics of the supine human and transport system would also benefit patient safety planners and vibration suppression designers in their endeavors.