Dual Mode Predictive Control for Active Flutter Suppression on an Aerofoil with Input Constraints

What is it about?

Flutter is a dynamic instability that can happen in an aircraft, happening through with the interaction between aerodynamic, elastic and inertial forces. It is a potentially catastrophic phenomenon, to the extent that it must be ensured that flutter does not occur in the flight envelope and that the aircraft is sufficiently controllable. For this purpose, active (or closed loop) control techniques can be adopted. In this context, different strategies were applied, such as PID or state feedback. However, this type of control law does not consider actuator’s restrictions, which can lead to inappropriate results considering input saturation. As an alternative for constraint handling, the present study proposes the adoption of the so-called dual mode model predictive controller. In particular, this control technique is implemented for flutter suppression in a typical airfoil section containing a flap in the trailing edge, taking into account input constraints. For this purpose, initially the system is modeled by considering unsteady effects, which were approximated through rational functions. Subsequently, by introducing delay terms, a linear model is obtained. This model is considered during the control system design, as well as the input increment and magnitude constraints. Simulation results show that the dual mode MPC is able to eliminate the flutter with proper enforcement of input constraints. In contrast, a traditional state feedback controller results on instability when such constraints are enforced by saturation.

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Photo by Kent Pilcher on Unsplash

Photo by Kent Pilcher on Unsplash