Adaptive Spatial Filtering for Aeroservoelastic Response Suppression

Abstract

Aeroservoelastic interactions have become a critical design consideration for meeting the increasingly demanding performance requirements imposed on aircraft designs. The traditional approach for establishing flight control system (FCS) stability margins is to use notch-filtering; this introduces phase lag that limits the FCS bandwidth, and may not be robust to changes in flight condition, aircraft configuration, or damage. We propose an adaptive spatial filtering approach that makes use of additional sensors to reduce aeroelastic interactions with the flight control system, allowing for increased control bandwidth, and greater robustness. A simple, computationally-efficient, and robust adaptation algorithm is used to optimize the spatial filtering as the system changes. A Lyapunov function is used to prove stability of the combined FCS and adaptive filter. The adaptive spatial-filtering approach is demonstrated on a simple aeroelastic model of a Boeing 747-SP, yielding attenuation of target modes of 20dB and higher without the phase lag associated with time-domain notch and low-pass filters. The ability to detect and track changes in the system is demonstrated. The adaptive spatial filter can be used in any application where minimizing control interactions with uncertain or time-variant structural dynamics is desired.

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