Design of piezostack-driven trailing-edge flap actuator for helicopter rotors

A piezoelectric actuator is investigated to activate a trailing-edge flap mechanism for helicopter vibration suppression. This paper presents the development of a piezostack-based actuator with a new stroke amplification mechanism. A double-lever amplification concept is introduced, which is a dual-stage lever-fulcrum stroke amplifier that extends the capability of the conventional lever-fulcrum mechanism. Both the design and fabrication of the on-blade trailing-edge flap actuator are addressed. The first prototype actuator was designed and fabricated using two piezostack segments. An amplification factor of 19.4 and constant response covering up to 8/rev (52.3 Hz) were measured under non-rotating conditions, and a consistent actuator displacement of up to 600g of centrifugal loading was experimentally obtained for the vacuum spin testing. A major design refinement resulted in the second prototype actuator that uses five piezostack segments. The bench-top testing of the second prototype actuator showed 1.87 mm (73.7 mil) of free stroke, and uniform performance of up to 150 Hz. In vacuum spin testing, the second prototype actuator showed approximately 13% loss in actuation stroke at 700g of centrifugal loading, and no further degradation at 115% overloading condition. The double-lever amplification mechanism with piezostack actuation showed the potential for operation in a rotating environment.