Extremum-Seeking Control of Subsonic Cavity Flow

An adaptive control system using extremum-seeking optimization is developed to suppress subsonic cavity How resonance. First, a simple but effective linear feedback control law is employed. This control law uses pressure fluctuations measured at two different cavity side-wall locations as feedback signals. The influence of the control parameters (namely, a gain K and a phase shift phi) on the magnitude of the limit cycle in closed loop is investigated analytically and experimentally. Second, an extremum-seeking algorithm is implemented to optimize in real time the selection of the most critical control parameter phi in such a way that the magnitude of the limit cycle is minimized in closed loop. The performance of the resulting control system is compared with that of a linear-quadratic feedback controller of fixed structure, developed on the basis of a reduced-order model of cavity flow dynamics. Experimental results highlight the advantage of parameter adaptation provided by the extremum-seeking algorithm over the controller of fixed structure under varying flow conditions.