This paper considers the problem of stabilizing a plant using a suboptimal stable compensator of fixed order. The resulting equations are a modified form of the optimal projection equations, with the separation principle not holding in either the full- or reduced-order case.
American Control Conference
Closed loop systems, Control systems, Frequency synthesizers
Abdallah, Chaouki T.; M. Jacobus; M. Jamshidi; Peter Dorato; and D. Bernstein. "Suboptimal strong stabilization using fixed-order dynamic compensation." American Control Conference (1990): 2659-2660. https://digitalrepository.unm.edu/ece_fsp/32