Kharitonov-Based Frequency Domain Bounds for Parametric Uncertainty in an Aeroelastic System

A methodology based on Kharitonov’s theorem is proposed to assess the impact of parametric uncertainty on a nonlinear aeroelastic airfoil system with three degrees of freedom. The system is linearized at an operating point defined by air velocity and pitch angle, and uncertainty is introduced on a structural stiffness parameter. The Kharitonov polynomials are applied to bound the system uncertainty in the gain-phase plane (Nichols chart). The method's conservatism, due to the assumption of decoupled parameters, is analyzed. This approach provides a framework for designing robust active flutter control systems that maintain stability in the presence of uncertainty.