FREQUENCY DOMAIN IDENTIFICATION OF THE HEAD-NECK COMPLEX

Abstract

The head-neck complex (HNC) responses to the trunk horizontal (fore and aft) vibration in the seated human body were studied. It was assumed that the HNC has only rotational motion in mid-sagittal plane. An experimental method was designed to generate the trunk horizontal vibration, and to measure the input and output signals to the system. The subjects were exposed to the random vibration at a magnitude of 1.60(ms)^<-2> rms (root-mean-square) for 50 seconds. The coherence and frequency response function were then obtained on 0.5 Hz to 10 Hz. The results manifested that the HNC behavior was quasi-linear with a dominant resonance frequency nearly between 1 Hz and 1.4 Hz. Accordingly, a two-dimensional single-inverted-pendulum was considered as a model for the HNC. Frequency domain identification method was then used to estimate the unknown parameters, including the HNC viscoelastic and inertia parameters. in the low Frequency range (<3HZ). The model was examined in the time domain using both random and sinusoidal vibration. Good agreement was obtained between experimental and simulation results.