Output Feedback Form and Adaptive Stabilization of a Nonlinear Aeroelastic System

Abstract

The question of output feedback representation and the design of a new adaptive control system for the control of an aeroelastic system using a single output feedback are treated. The chosen dynamic model describes the nonlinear plunge and pitch motion of a wing. The parameters of the system are assumed to be completely unknown. For the derivation of control law, the existence of output feedback forms of the model is examined. It is shown that for the choice of pitch angle as an output, an output feedback form of the system can be derived, but this kind of representation is not possible if the plunge displacement is chosen as an output. As such, adaptive control of the aerolastic model based on the backstepping design technique by plunge displacement feedback is not feasible. Then a global diffeomorphism is constructed for obtaining an output feedback form'of the model when the pitch angle is the output. Based on this output feedback form and a backstepping design technique, an adaptive control law for the trajectory control of the pitch angle is derived. For the synthesis of the controller, only the pitch angle is used. It is shown that, in the closed-loop system, pitch angle trajectory control is accomplished and that the state vector asymptotically converges to the origin in spite of the uncertainties in the model using only pitch angle feedback.