Adaptive Feedback Linearisation and Control of a Flexible Aircraft Wing

Abstract

Active control systems are used on aircraft to reduce loads due to gusts and manoeuvres, reduce the effect of noise, and could also increase the speed at which flutter occurs. Unfortunately most aeroservoelastic systems include some form of nonlinearity, and this increases the complexity of the feedback system and also facilitates the likelihood of Limit Cycle Oscillations occurring. Previous work on the application of Adaptive Feedback Linearisation to aeroelastic systems has demonstrated the promising potential of this method when applying control in the presence of substantial nonlinearity. In this work, Adaptive Feedback Linearisation is applied to an aeroelastic model of a cantilevered flexible wing with a cubic hardening structural nonlinearity in an engine pylon. Using assumed vibration modes, a suitable model of the wing is developed, into which structural nonlinearity is incorporated. Closed-loop control is implemented on the aeroservoelastic system via linearising feedback computed through the Adaptive Feedback Linearisation algorithm. The advantage of the latter is the guaranteed stability of the closed-loop aeroelastic system, despite lack of knowledge of the exact description of the nonlinearity. It is shown how such an approach can be used to delay the onset of flutter or limit cycle oscillations.