Retrospective cost adaptive control of low-reynolds number aerodynamics using a dielectric barrier discharge actuator

The performance of micro air vehicles (MAVs) is sensitive to flow unsteadiness such as wind gusts, due to their low flight speed and light weight. We investigate the interplay of active flow control and stable flight performance. Specifically, a dielectric barrier discharge (DBD) actuator, characterized by fast response and non-moving parts, is used to control unsteady aerodynamics under fluctuating free-stream conditions on finite and infinite wings with the SD7003 airfoil geometry at chord Reynolds numbers between 300 and 1000. Feedback control is achieved using a retrospective cost adaptive controller, which adjusts control gains by minimizing a quadratic function of the retrospective performance and requires knowledge of nonminimum-phase (NMP) zeros (i.e., the complex numbers with magnitude greater than one where the transfer function equals zero) of the linearized flow-actuator model. The linearized flow-actuator system with lift as the performance has one real NMP zero, which approaches one as the distance between the actuator and the leading edge, Reynolds number, wing aspect ratio, or voltage increment decreases. At 15° angle-of-attack under modest free-stream fluctuation, DBD actuator commanded by the control law can stabilize lift by adjusting pressure and suction regions on the airfoil surface.