Terfenol-D-driven flaps for helicopter vibration reduction

ABSTRACT The utility of helicopter aviation is limited by the high vibration levels caused by interaction of each rotor blade with the wake of preceding blades. Existing full blade actuation using a swashplate has various problems such as insufficient bandwidth, limitations in the number of harmonics controlled, high maintenance, and lack of spanwise lift variation. Theseproblems are avoided by the proposed flap operated, individual blade control system, which uses magnetostrictive actuation technology. Terfenol-D actuation has many advantages over competing technologies such as hydraulic systems, electricmotors, and piezoelectric elements. These benefits include a1lelectric operation, simplicity and reliability low mass, low voltage, and insensitivity to centripetal acceleration. A blade mounted Terfenol-D actuator was developed for the high weightpenalty helicopter application. The optimum coil to Terfenol-D volume ratio was derived that gives the highest mechanical power output for a small actuator envelope and mass. A fixed ability to dissipate coil resistive losses is assumed. The