Influence of Occupant Compliance on a Vertically Stroking Helicopter Crew Seat Suspension

Abstract

This study addresses the effects of compliance of an occupant seated in an adaptive seat suspension equipped with a magnetorheological energy absorber, and exposed to intense vertical shocks. A 50th percentile male occupant, exposed to shock conditions characterized by sink rates varying from 5 to , was considered. The compliance effects were examined by comparing the response of a multiple degree-of-freedom biodynamic lumped-parameter model derived from the response of a Hybrid II anthropomorphic test dummy representing a compliant-occupant model to the response of an equivalent rigid-occupant model under the same shock conditions. An experimentally validated nonlinear mathematical model of a magnetorheological energy absorber was integrated with both the compliant and rigid models of the occupants. In addition, three different control techniques were investigated based on controlling the onset of magnetorheological-energy-absorber stroking load: constant stroking-load control, terminal trajectory control, and optimal control. The internal damping of a compliant occupant proved to be a crucial parameter in determining the biodynamic response for all control techniques. An assessment of the potential of injury was conducted based on the established injury criteria for compliant occupants to evaluate the applicability of the control techniques.