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

A hybrid design approach for low vibration systems is studied. Active trailing edge flap design is integrated with blade structural optimization. The finite element method is used to model the rotor undergoing elastic deflections in flap, lag and torsion. Aerodynamic loads generated by the trailing edge flap are calculated using classical incompressible theory. For a given set of blade structural properties and active flap control, a coupled propulsive trim is implemented to simultaneously determine the blade nonlinear response, vehicle orientation and helicopter control settings. An integrated optimal control/optimization process is developed to simultaneously determine the active control efforts and optimal passive blade structural parameters. The objective of the optimization is to simultaneously minimize the hub vibratory loads and active flap control angles by selecting the optimum passive design parameters. The study shows that retrofitting an active flap to a baseline blade or to an optimal passive blade configuration might not provide us with the best result. It is shown that the active-passive hybrid method can outperform these configurations and achieve more vibration reduction with less control efforts.