Robust stabilizability for linear systems with both parameter variation and unstructured uncertainty

This paper considers the problem of finding one compensator which stabilizes a plant having both parameter variation and high frequency unstructured uncertainty. A new uncertain system model is proposed to characterize plants containing those two different uncertainties. Closed loop stability criterion is then derived for the new model. To obtain the desired results, number of assumptions describing the set of allowable plants are imposed. The satisfaction of these assumptions guarantees the existence of a proper stabie compensator C(s) achieving robust stabilization. The algorithm used for controller design has some most attractive features: Namely, it is recursive in nature and allows the designer to select one compensator coefficient at a time. Also, the construction of the compensator depends on the difference between the orders of numerator and denominator polynomials of the nominal plant and often leads to a lower order compensator.