Koopman-based model predictive control with morphing surface: Regulating the flutter response of a foil with an active flap

Active flow control can achieve substantial performance gains and meet the challenges of next-generation air vehicles and energy-harvesting devices. The use of active flow control techniques with the moving flap or morphing surfaces has been shown to be a viable path to regulating the flow-induced vibration of the foil. However, due to the complex nature of flow over morphing surfaces, all physical phenomena are intertwined, which prevents a clear understanding of the underlying flow physics and, therefore, a successful design of a controlling action to optimally modify them. In this research an active flow control framework with the model predictive control theory is proposed to modulate the flow-induced flutter of a foil using the morphing flap surface. The geometrically weighted dynamic-relevant modes are used to build surrogate models to achieve rapid model-based active control of complex systems. It is shown that the flap is capable of both facilitating and eliminating fluid-induced vibrations by regulating the lift forces exerted on the foil. Furthermore, the control framework provides full knowledge of how the structure modifies the flow and has the potential to identify the ambient environmental change simultaneously.