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 con trol 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 airw orthiness 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 desig ning a minimum weight actuator, subject to a set of actuation and stress co nstraints. An important ingredient in this design process is the precise ch aracterization of the constitutive relations for the magnetostrictive mater ial which provides valuable guidelines on the practical implementation of m agnetostrictive actuators. It is shown that the magnetostrictively actuated flap is capable of producing vibration reduction in high speed forward fli ght in excess of 90%. (C) 2001 Elsevier Science Ltd. All rights reserved.