Active control of the onset of stall instabilities in axial how compre
ssion systems is pursued using bifurcation analysis of a dynamical mod
el proposed by Moore and Greitzer. The state variables of this model a
re the mass Row rate, pressure rise, and the amplitude of the first-ha
rmonic mode of the asymmetric component of the how. A subcritical pitc
hfork bifurcation is found to occur at the inception of stall, resulti
ng in a large-amplitude instability and associated hysteresis behavior
. Using the throttle opening of the compression system for actuation,
it is found that the eigenvalue that becomes zero at the onset of stal
l is linearly uncontrollable. This, along with uncertainty of the post
-stall linearized model, motivates a consideration of nonlinear feedba
ck control laws for mitigation of the jump and hysteresis behavior occ
urring at stall onset. Following the bifurcation control calculations
introduced by Abed and Fu [Abed, E. H. and J. H. Fu (1986). Local feed
back stabilization and bifurcation control, I. Hopf bifurcation. Syst.
Control Lett, 7, 11-17. and Abed, E. Ii. and J. Fl. Fu (1987). Local
feedback stabilization and bifurcation control, II. Stationary bifurca
tion. Syst. Control Lett, 8, 467-473], it is found that feedback incor
porating a term quadratic in the first-harmonic flow asymmetry variabl
e renders the pitchfork bifurcation supercritical. This introduces a n
ew stable equilibrium near the nominal equilibrium after the nominal e
quilibrium itself has lost stability, thus eliminating the undesirable
jump and hysteresis behavior of the uncontrolled system.