Novel, High-Authority Flap Actuation Concepts using Single Crystal Stacks

Conventional piezoelectric ceramic flap actuators have exhibited inadequate levels of stroke and/or force required to produce an angle of rotation in excess of ±6° at 40 Hz. Single crystals represent a revolutionary advance in piezoelectric actuator technology. Because crystal electromechanical properties are significantly different than those of ceramic, it should be expected that the use of crystals requires motion amplification techniques that are tailored to crystal behavior. This proposal describes a new, high authority trailing edge flap actuator concept for helicopter rotor blade vibration control that has been specifically designed for single crystal stack actuators. Invercon has analytically and experimentally evaluated the feasibility of using single crystals together with a novel, high-moment, high-displacement, buckling beam flap actuator concept, which is well-suited for single crystal stack actuation. Experimental results show that the buckling beam actuator can dramatically outperform state-of-the-art flap actuators, such as the X-frame, with the capability of displacing a 36 “ flap ±5º at 40 Hz under representative aerodynamic loading at 400 RPM. Such actuators also consist of less parts, and are significantly lighter than existing designs. The technology developed in Phase II will enable future Army technologies such as swashplateless rotors and trailing edge flaps for heavy lift rotorcraft.