Aircraft structures, specifically wings, are inherently flexible, resulting in aeroelastic interactions between the deformed configuration and the aerodynamic forces acting on it. One such aeroelastic interaction is flutter – a self-sustained oscillation phenomenon that often leads to structural failure. Since flutter might be destructive, it is commonly avoided by restricting the flight envelope to flutter-free regions. Flutter in the flight envelope can be avoided by using Active Flutter Suppression (AFS) technologies that push the flutter onset to higher dynamic pressure values. Several recent studies investigated the use of linear control design methods in AFS systems, where the design method for the controller includes optimal and robust control techniques. The major drawback of those methods is that they are limited to linear design models and requirements.
The current study focuses on developing a method for linear controller synthesis that accounts for nonlinear design specifications. This is done using external nonlinear optimization that modifies the synthesis set-up to achieve improved (nonlinear) performance and selection of an optimal controller via Genetic Algorithm (GA) optimization. The method is demonstrated on the Active Aeroelastic Aircraft Testbed (A3TB), a flying-wing UAV platform that experienced flutter in flight. The seminar will present the aeroelastic modelling of the aircraft, aeroservoelastic analyses, nominal AFS controller design, and GA-based controller tuning. The optimization was successfully performed, increasing the flutter speed onset of the closed-loop system from 29 to 61 m/s, which is outside the flight envelope.