General Extended State Observer-Based Robust Integral of Signum of Error Controller for Active Flutter Suppression for Aeroelastic System

The paper presents a robust integral of signum of error (RISE) controller for active suppression of flutter of a two-dimensional airfoil, and it is integrated with a general extended state observer (GESO). Toward this, airfoil model in state space is first changed into a canonical form. Then, the controller is designed using RISE control technique. As equations of system dynamics are not into integral chain form, a GESO is formulated to observe system states and disturbances. The controller is implemented using estimated states and it is robustified using estimated disturbance. Stability of the proposed general extended state observer-robust integral of signum of error (GESO-RISE) controller is established using the Lyapunov theory. Simulations are performed to check the proposed controller's performance against variations in airspeed, uncertainties in model parameters, external disturbances, time delay, and unmodeled dynamics. Comparison of the proposed GESO-RISE controller is carried out with existing controllers using two performance criteria, i.e., Control Efforts (CoE) and integral of absolute error (IAE). It is discovered from simulations that the proposed GESO-RISE controller significantly reduces IAE and control efforts. Additionally, Monte Carlo method is utilized to check robustness of the proposed GESO-RISE controller. The proposed GESO-RISE controller significantly enhances flutter boundary of airfoil and is completely implementable.