The design of a control law for rotating stall in an axial compressor

Presented in this paper is the design of a control law for rotating stall in axial compressors. The controller design is executed in two primary phases. In the first phase, an input-output model of the compressor is developed to recover the frequency response of the spatial mode dynamics. The representation of the compressor dynamics in this form facilitates the controller design process. In the second phase, a feedback controller having the structure U_i = K_ie^iβiy_i is designed to maximize the stability of the i_th spatial mode where y_i denotes the i_th spatial harmonic. Maximum performance is limited by the output saturation of the air injectors. The design of K_i and β_i is realized using a feedback control notion referred to as sensitivity. Sensitivity is a measure of the transmissibility of the disturbances which lead to rotating stall. The controller is designed for an analytical compressor model comprised of nonlinear ordinary differential equations (NODE). These NODEs are derived from a reduction of the Moore-Greitzer partial differential equations (PDE). The paper concludes with a discussion of designing dynamic controllers which may achieve performance beyond the control law U_i = K_ie^iβiy_i..