Adaptive Feedforward Control for Gust Load Alleviation

Abstract

In this paper, an adaptive feedforward control framework is proposed for the suppression of aircraft structural vibrations induced by gust perturbations to increase the resilience of the !ight control law in the presence of the aeroelastic/aeroservoelastic interactions. Currently, aircraft with nonadaptive control laws usually include roll-off or notch lters to avoid aeroelastic/aeroservoelastic interactions. However, if changes in the aircraft conguration aresignicant,the frequencies of the!exible modesof the aircraft may beshifted, andthe notchlterscould become totally ineffective. With the proposed approach, the !exible modes can be consistently estimated in real time via a proven system-identication algorithm. The identied !exible modes information is used in the proposed adaptive feedforwardcontrolalgorithmtoadjusttheparametrizationofthebasisfunctionsinafeedforwardcontroller.Along with the recursive least-squares estimate, the feedforward controller is adjusted, and the structural vibration of the aircraft induced by the gust perturbation can be largely suppressed. An F/A-18 active aeroelastic wing aeroelastic model with gust perturbation based on the linear aeroelastic solver formulation is developed as a test bed to demonstrate the proposed adaptive feedforward control algorithm.