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 con"guration aresigni"cant,the frequencies of the!exible modesof the aircraft may beshifted, andthe notch"lterscould become totally ineffective. With the proposed approach, the !exible modes can be consistently estimated in real time via a proven system-identi"cation algorithm. The identi"ed !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.

/pdf/adaptive-feedforward-control-for-gust-load-alleviation-56rj3k4n4j.pdf

Adaptive Feedforward Control for Gust Load Alleviation

This paper introduces an adaptive flutter suppression contr ol algorithm which is based on the iterative estimate of the aeroelastic plant and design of the feedback controller. In this algorithm, the dual-Youla parametrization is implemented as an essential part to estimate the open loop aeroelastic model from the closed loop experiment. The advantage of utilizing the dual-Youla parametrization for the aeroelastic plant estimation is that the possible unstable open loop aeroelastic model could be estimated in the situation where aeroelastic dynamic system is operating above the flutter sp eed. Based on the estimated open loop model, a new controller could be designed using the standard controller design techniques to extend the flutter envelope boundary. By iteratively estimating the open loop aeroelastic model and designing the controller, the flutter boundary could be expanded. Application of this adaptive control algorithm to the pitch-plunge aeroelastic system shows that the flutter boundary can be expanded by 80%.

/pdf/adaptive-feedback-control-algorithm-for-flutter-boundary-2farwd3ycz.pdf

Adaptive Feedback Control Algorithm for Flutter Boundary Expansion

Flutter Analysing Over an Aircraft Wing During Cruise Speed

Adaptive Feedforward Control for Gust Loads Alleviation

Review of Aeroelasticity Testing Technology

A gain-scheduled controller for active flutter suppression of the NASA Langley Research Center's Benchmark Active Controls Technology wing section is presented. The wing section changes significantly as a function of Mach and dynamic pressure and is modeled as a linear system whose parameters depend in a linear fractional manner on Mach and dynamic pressure. The resulting gain-scheduled controller also depends in a linear fractional manner on Mach and dynamic pressure. Stability of the closed-loop is demonstrated via time simulations in which both Mach and dynamic pressure are allowed to vary in the presence of input disturbances. The linear fractional gain-scheduled controller and an optimized linear controller (designed for comparison) both achieve closed-loop stability throughout the operating region.

P.A. Blue

Papers

Active flutter suppression via gain-scheduled linear fractional control