Stabilization of singularly perturbed linear time-invariant systems using low-order observers

Singularly perturbed linear time invariant systems with inadequately modeled, but stable fast dynamics are considered. Conditions are formulated under which a reduced-order observer can be designed for estimating the "slow" states from a knowledge of only the degenerate model. A design methodology, which is robust with respect to the neglected "fast" dynamics, is presented for stabilizing systems satisfying these conditions. Finally, an illustrative example for the autopilot-actuator system design for controlling the lateral motion of an aircraft is given.