Magnetostrictively actuated control flaps for vibration reduction in helicopter rotors—design considerations for implementation

Vibration reduction using blade root pitch control introduces a significant power penalty and may adversely affect the airworthiness of the flight control system. Comparable levels of vibration reduction can be achieved using considerably less power through an actively controlled trailing edge flap mounted on the blade. Such a device would have no effect on helicopter airworthiness since it is controlled by a loop separate from the primary flight control system which utilizes the swashplate. Control flap actuation using the magnetostrictive material Terfenol-D is studied in this paper by designing a minimum weight actuator, subject to a set of actuation and stress constraints. An important ingredient in this design process is the precise characterization of the constitutive relations for the magnetostrictive material which provides valuable guidelines on the practical implementation of magnetostrictive actuators. It is shown that the magnetostrictively actuated flap is capable of producing vibration reduction in high speed forward flight in excess of 90%.