Active-passive hybrid optimization of rotor blades with trailing edge flaps

A hybrid design method, focused on reducing vibration while minimizing control effort, is developed. In this integrated active-passive approach, trailing edge flap controller design is combined with blade structural optimization. An aeroelastic model is developed for a helicopter rotor with a trailing edge flap. The objective function, which includes vibratory hub loads and active flap control inputs, is minimized by an integrated optimal control/structural optimization process. It is demonstrated that both the hub vibratory loads and active flap control effort can be reduced. The study shows that retrofitting an active flap to a baseline blade or to an optimal passive blade configuration might not be an effective design approach. The active-passive hybrid method can outperform these configurations by achieving more vibration reduction with less control effort. The hybrid design procedure can reduce the required active flap deflections by about 30-60% in the whole flight range. An analysis and parametric study of the hybrid design of rotor blades with trailing edge flaps is conducted. The off-design condition for hybrid approaches is examined and the robustness of the hybrid design is addressed. The physical understandings of the hybrid design are explored.