Gain-Scheduled Higher Harmonic Control for Full Flight Envelope Vibration Reduction

This paper investigates the dynamics of the SMART rotor, and presents a method to design a gain-scheduled controller to reduce the harmonic vibration throughout the flight envelope. The dynamics of the SMART rotor was examined at various flight conditions through nonlinear simulation. The simulation results showed that the dynamics is strongly dependent on the advance ratio, but only weakly dependent on the blade loading and the rotor shaft angle. To reduce the higher harmonic vibration throughout the flight envelope, a controller gain-scheduled on the advance ratio is presented. Output from linear time-invariant higher harmonic controllers designed for different flight conditions are blended to form the gain-scheduled controller. Closed-loop simulations of the helicopter rotor undergoing transitional flight with increasing advance ratio were conducted. The results from the closed-loop simulations show that the 5 per rev normal vibration was reduced by over 97% at the rotor hub.