On the structure of suboptimal \(H^ \infty\) controllers in the sensitivity minimization problem for distributed stable plants (Q1175522)

The authors apply the theory of Foias-Tannenbaum to describe the set of all suboptimal \(H\)-infinity controllers in the sensitivity minimization of a class of distributed parameter plants. For stable plants with continuous transfer functions finite-dimensional suboptimal controllers can be obtained by approximating the infinite-dimensional part of the optimal controller. Advances of this procedure over first approximating the plant with a finite-dimensional plant and then solving the sensitivity minimization problem for this approximate plant are discussed. The results are applied in particular to delay systems. Earlier work of Lenz-Ozbay-Tannenbaum-Turi-Morton considered the problem for the case of a flexible beam.