Dynamics of active biomechanical models of seated human body and their vibration isolation systems

Abstract

In the paper the dynamic behaviour of the systems composed of active human body models (AHBM) and passive isolation systems (VIS) subjected to sinusoidal and random excitations was discussed. The two active human body biomechanical models («back-off» and «back-on») obtained several years ago by the first author of the presented paper can be considered as active, linear, stable, lumped parameter and unidirectional dynamical systems. These models «seated» on passive vibration isolation systems (VIS) make new, coupled dynamical models (AHBM+VIS). In the first part of the presented paper the dynamical characteristics of the coupled, linear models (AHBM+VIS) were thoroughly analyzed. The new maps of poles distribution of characteristic equations of the systems composed of the coupled models show, that in some cases, these systems can be unstable. In the paper the stability areas were numerically estimated and graphically presented for the simplest, linear vibration isolation system. In the second part of the paper the influence of some chosen nonlinear elements injected into VIS on the amplitudes of chosen model mass accelerations and relative displacements between them was estimated, basing on the results obtained from the simulation approach. The simulation investigations were done for a sequence of time delay of the VIS reactions and sinusoidal excitations. The sinusoidal excitations had variable amplitudes and the frequencies corresponding to the first resonant frequency of the considered AHBM+ VIS systems. The values of the corresponding amplitudes of output signals were compared. In chosen cases where the simulations were done for the random excitations the root mean square values of the output signals were compared. The obtained results were compared with the simplest linear VIS, graphically presented and discussed. W pracy przeprowadzono analizę numeryczną własności dynamicznych układu składającego się z aktywnego modelu biomechanicznego ciała siedzącego człowieka (AHBM) oraz pasywnego układu wibroizolacji (VIS) w wersji liniowej i nieliniowej, poddanego wymuszeniom harmonicznym i przypadkowym. Rozpatrzono dwie wersje modelu ciała siedzącego człowieka. Przeprowadzono numeryczną analizę stabilności układów AHBM - VIS w wersji liniowej. Na podstawie analizy symulacyjnej porównano wpływ wybranych nieliniowości wchodzących w skład pasywnego układu wibroizolacji (VIS) na wartości wybranych sił, przyspieszeń i przemieszczeń względnych układu całego układu AHBM - VIS.