Output Feedback Variable Structure Adaptive Control of an Aeroelastic System

Abstract

The paper presents an application of the variable structure model reference adaptive control theory to control of aeroelastic systems with structural nonlinearity. Interestingly, the design approach does not require any knowledge of the parameters of the system and the nonlinear functions, and only output feedback is used for the synthesis of the control systems. Control laws for the trajectory tracking of pitch angle and plunge displacement are derived. In the closed-loop system, the state vector asymptotically converges to the origin. Control laws are discontinuous functions of the tracking error, and modulation functions of the relays are generated on-line using bounds on uncertain functions and certain auxiliary signals. Digital simulation results are presented which show that in the closed-loop system, pitch angle and plunge displacement are smoothly regulated to zero in spite of the uncertainty and unmodeled functions in the system using only output feedback.