Effectiveness of Direct and Hybrid Piezoelectric Control for Whirl Flutter

Whirl flutter plays an important role in the current aeronautical scenario. Due to the advent of modern air mobility, more efficient propeller-driven aircraft have been sought. This type of aircraft is susceptible to such a phenomenon, as it can influence performance and operational life, cause undesirable behaviors and failures, and affect the design of wings, nacelles, and rotors. Thus, increasing the stability margins by controlling this phenomenon should be explored. This research investigates piezoelectric passive and hybrid control in a representative two-degree-of-freedom rotor-nacelle model, examining the effects of cubic structural hardening. First, the stability of the linear aeroelastic and piezoaeroelastic systems was obtained via the eigenvalue problem. For the nonlinear system, the Hopf bifurcation was explored. The results indicate that the passive control can be suitable to postpone the whirl flutter occurrence. However, the subcritical behavior could take place for some specific bimorph configurations. This undesirable behavior could be overcome by applying the hybrid control via time-delayed feedback. Besides the better ability to increase the flutter speed than the passive control, the hybrid control could convert the subcritical into supercritical behaviors.