Semi-active control of vertical stroking helicopter crew seat for enhanced crashworthiness

A control algorithm is presented through which a magnetorheological energy absorber may be used in a crew seat suspension to automatically accommodate occupants of varying weight. A nonlinear lumped parameter model of a seated occupant was coupled with the nonlinear Bingham-plastic force model for an MREA. This lumped parameter model assumes the human is seated and that 29% of the body weight is supported by the feet and the body is divided into four parts including, pelvis, upper torso, viscera, and head. The load-limiting control, however, prevents the total force imparted into the seat from exceeding the limit value by modulating the yield force. It can also be seen that limiting the load to 14.5 G efficiently uses more of the available stroke than the constant yield force case.