Semi-active magnetorheological helicopter crew seat suspension for vibration isolation

This study explores the use of magnetorheological dampers in a semi-active seat suspension system for helicopter crew seats to enhance occupant comfort. Key concepts in designing a magnetorheological seat suspension system to isolate the occupant from rotorcraft vibration are identified. Using these design concepts, a magnetorheological damper is designed, fabricated, and retrofitted into a tactical SH-60 Seahawk crew seat. This magnetorheological damper is implemented in series with the existing fixed load energy absorbers such that the crashworthiness capability of the seat is not impaired. Semi-active control is implemented and performance is evaluated both analytically and experimentally. Experimental test results have shown that this system reduced the dominant rotor-induced vertical vibration (4 per rev) transmitted to a 50th percentile male aviator by 76%, which is a 61-70% improvement over the unmodified SH-60 crew seat depending upon whether a soft seat cushion is used. Furthermore, these experimental tests also show that this system significantly reduces vertically induced seat rocking that occurs as a result of an offset center of gravity in the crew seat design.