Adaptive Feedforward Control for Gust Load Alleviation

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 flight control law in the presence of the aeroelastic/aeroservoelastic interactions. Currently, aircraft with nonadaptive control laws usually include roll-off or notch filters to avoid aeroelastic/aeroservoelastic interactions. However, if changes in the aircraft configuration are significant, the frequencies of the flexible modes of the aircraft may be shifted, and the notch filters could become totally ineffective. With the proposed approach, the flexible modes can be consistently estimated in real time via a proven system-identification algorithm. The identified flexible modes information is used in the proposed adaptive feedforward control algorithm to adjust the parametrization of the basis functions in a feedforward controller. 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.