Active Flutter Control with a V-Stack Piezoelectric Flap Actuator

Abstract

Aeroelastic control of wings using distributed, trailing-edge control surfaces is of interest for maneuvers, gust alleviation, and flutter suppression. The use of high-energy-density, piezoelectric materials as motors provides an appealing solution to the problem of flutter suppression. A new piezoelectric actuator, the V-stack piezoelectric actuator, was designed and bench tested at Duke University. This actuator meets the requirements for trailingedge flap actuation in both stroke and force. It is compact, simple, and sturdy and leverages stroke geometrically with minimum force penalties while displaying linearity over a wide range of stroke. Integration of the actuator inside a structure requires minimal modifications. The shape of the actuator makes it extremely suitable for trailing-edge flap actuation, eliminating the need for a push rod. A typical section prototype was constructed and tested experimentally in the wind tunnel at Duke University. This experiment was designed for preliminary evaluation of the actuation concept. During bench tests the desired flap deflection of ±5 deg was obtained. Windtunnel experiments showed that air flow has little influence on flap deflection, suggesting good actuation authority. Actuator-flap frequency bandwidth achievable for this experiment, in the context of ±5 deg flap deflection, was sufficient and facilitated control design. Positive position feedback (PPF) control was used to add damping to the unstable flutter mode. Operating in closed loop, the flutter was suppressed at the speed at which the flutter occurred open loop, and the flutter speed was increased by more than 30%.