Extremum-Seeking Control of Subsonic Cavity Flow

An adaptive control system using extremum-seeking optimization is developed to suppress subsonic cavity flow oscillations. The overall control system is developed by following two steps. First, a simple linear control law which uses measurements of wall pressure fluctuations at two different locations in the cavity is developed, and the effect on the magnitude of the limit cycle produced by tuning its control parameters, namely a gain K and a phase shift φ, is investigated analytically and experimentally. Then, an extremum-seeking algorithm is implemented to optimize the selection of the most critical control parameter, φ, in real time, in such a way that the magnitude of the limit cycle is minimized in closedloop. A comparison with a linear-quadratic feedback controller based on a reduced-order model of the flow dynamics is presented and discussed. Experimental results highlight the advantage of parameter adaptation provided by the extremum-seeking algorithm over controllers of fixed structure when operating in off-design conditions.