A Nonlinear Output Feedback Regulation Method for Limit Cycle Oscillation Suppression Using a Sliding Mode Observer

A nonlinear output feedback control method is presented, which achieves asymptotic limit cycle oscillation (LCO) regulation in an aircraft wing section using synthetic jet actuators. To eliminate the standard requirement that LCO pitching and plunging rates are available for feedback, a finite-time sliding mode observer is utilized to estimate the rates using only measurements of LCO displacements. To achieve the result, a detailed mathematical model of the LCO dynamics is utilized, which includes nonlinear stiffness effects, unmodeled external disturbances, and dynamic model uncertainty, in addition to the parametric actuator uncertainty. A rigorous analysis is used to prove finite-time convergence of the estimation error, and a Lyapunov-based stability analysis is used to prove asymptotic regulation control of the LCO. Numerical simulation results are also provided which show the performance of the proposed sliding mode observer-based control design in comparison with our recently developed bank of filters-based output feedback LCO control method.