Adaptive Control of Aircraft Wing Flutter by Stress-Induced Stiffness Modification

Abstract

Lightweight unoccupied air vehicles (UAVs) with wide wingspans are especially vulnerable to dynamic instability. Such instability can be contained by using mass and stiffness balancing and the shape and attitude of the aircraft in flight. Passive methods and pilot-operated devices such as dampers, ailerons, flaps, and other actuators, are currently used. Also, ongoing attempts exist to develop self-adaptive controls by using piezoelectric and other devices. The present work is concerned with controlling aerodynamic flutter by using stress-induced elements in selected structural components of the aircraft wing. A scheme has been developed to determine the “optimal” locations for such elements to be activated, in real time, to contain the dynamic instability or flutter condition. Various stress-induced stiffening schemes have been developed to modify the frequency response of aircraft wings by shifting the critical flutter speed to safe levels. Results and conclusions include the identification of the optimal location and type of the stress-induced elements and the magnitude and distribution of induced stress for best results with the least expense of energy during actuation.