Development of a resonant trailing-edge flap actuation system for helicopter rotor vibrationcontrol

Abstract

A resonant trailing-edge flap actuation system for helicopter rotors is developed andevaluated experimentally. The concept involves deflecting each individual trailing-edge flapusing a compact resonant piezoelectric actuation system. Each resonant actuation systemyields high authority, while operating at a single frequency. By tailoring the naturalfrequencies of the actuation system (including the piezoelectric actuator and the relatedmechanical and electrical elements) to the required operating frequencies, one can increasethe output authority. The robustness of the device can be enhanced by increasing the highauthority bandwidth through electric circuitry design. Such a resonant actuation system(RAS) is analyzed for a full-scale piezoelectric induced-shear tube actuator, and bench-toptesting is conducted to validate the concept. An adaptive feed-forward controller isdeveloped to realize the electric network dynamics and adapt to phase variation. Thecontrol strategy is then implemented via a digital signal processor (DSP) system. Analysisis also performed to examine the rotor system dynamics in forward flight withpiezoelectric resonant actuators, using a perturbation method to evaluate thesystem’s time-varying characteristics. Numerical simulations reveal that the resonantactuator concept can be applied to forward flights as well as to hover conditions.