Stability, stabilisation and performance of multilevel controllers under structural perturbations. Part 2: Stabilisation under any structural perturbation

In this second part of the paper we study the stability and performance of two-level controllers subject to structural perturbations. The perturbations that are now considered could arise either from the failure of links between the two levels, as in Part I, or from failure of some of the physical interconnections between the subsystems. In addition, the stabilisation of the system is studied and bounds are also developed for the performance degradation. The latter compare the performance of the perturbed system to the globally optimal one.