Individual Blade Control for Component Load Alleviation Using Higher-Order Linear Time-Invariant Models.

This paper explores the synthesis of a novel load alleviation scheme based on active rotor control for critical helicopter component life extension. The proposed load alleviation scheme is innovative as it demonstrates how individual blade control (IBC) and model prediction can be combined using higher-order linear time-invariant models to develop a life-extending control scheme. Using a reduced-order coupled body-rotor-inflow dynamic model onboard the vehicle and a cost function, cost-minimizing higher harmonic IBC inputs are computed over a selected time horizon and used to reduce selected harmonics of component loads during flight. The proposed component load alleviation using the IBC scheme is implemented in a comprehensive nonlinear model of a generic helicopter to evaluate its performance. Nonlinear model simulations show that significant individual harmonic load reduction can be obtained with very little impact on the maneuver performance, vibratory hub loads, and uncontrolled harmonics of component loads. Furthermore, using the handling qualities requirement on small-amplitude pitch changes in forward flight, alongside the pitch attitude and agility quickness metrics, it is demonstrated that the proposed scheme does not cause handling qualities degradation. [ABSTRACT FROM AUTHOR]