Robustness of control design for axial flow compressors

Feedback control has been pursued to address the rotating stall problem in axial flow compressors in order to extend the stable operating range and to improve engine performance. These controllers guarantee the stability of the bifurcated operating solution near the stall point. However, how robust these controllers could be is still not clear. In this paper, local robust analysis is considered as a method to evaluate feedback control design for rotating stall. In particular, the set of admissible uncertainty is characterized analytically in terms of feedback control gain so that it is possible to compare the robustness of controllers with different feedback gains and select a proper robust controller for axial flow compressors. Indeed, since the characterization conditions of the uncertainty set are computable, the size of the set could then be 'computed' out so that a robust controller, which should tolerate a 'larger' uncertainty set, could be identified.