Blade-Vortex Interaction Control Methodology Based on Two Dimensional Analysis

The aim of the present work is the presentation and application of a methodology for the identification of multi-cyclic higher harmonic actuation of blade pitch motion suited for the alleviation of BVI loads, and hence of BVI noise annoyance generated by helicopter main rotors in lowspeed descent flight. The blade pitch actuation is defined by a feedback control law obtained through an optimal control approach based on the minimization of a cost function. In particular, first, strong BVI phenomena occurring in the specific flight condition are simulated as equivalent two-dimensional, multi-vortex, parallel BVI problems, and then a local controller methodology is applied for the efficient identification of the closed-loop control algorithm. This control synthesis methodology is validated by application of the identified gain matrices to a realistic helicopter main rotor in descent flight, and preliminary results concerning its capability to alleviate blade loads and emitted noise are presented and discussed.