Tiltrotor Wing-Root Vibratory Loads Reduction Through Higher Harmonic Control Actuation

This paper deals with the application of a via-swashplate Higher Harmonic Control for the reduction of vibratory loads transmitted to tiltrotor fuselage by the proprotor-pylon-wing system. The control laws are derived through a quadratic optimal control methodology, based on the predictions given by an aeroelastic simulation tool developed in the past by the authors. It uses nonlinear beam theory to model the structural behavior of proprotor blades and wing, and a potential-aerodynamics boundary element approach suitable to capture body-vortex interactions effects to evaluate wake inflow. Considering a XV-15 like configuration in airplane and helicopter mode flight, the numerical investigation examines different strategies in the identification of the optimal control law, analyzing their effectiveness and robustness in reducing the wing-root vibratory loads.