Control of compressor rotating stall without distributed sensing using bifurcation stabilization

Control of rotating stall in axial compressors is considered. A local bifurcation stabilization theorem using the projection method for the case of an uncontrollable, unobservable critical mode is described and extended to control laws that do not vanish at the critical or bifurcation point. This result is used to derive sufficient conditions for several control laws to guarantee that the subcritical pitchfork bifurcation of an axial compressor model is made supercritical so that the rotating stall hysteresis is eliminated. Each of the control laws considers operation at a set point distinct from the critical point and depends only on annulus-averaged quantities as feedback variables to simplify sensing and signal processing requirements. A numerical example shows the transformation of the bifurcation from subcritical to supercritical and the elimination of the hysteresis region