On Robust Stability and Performance With Time-Varying Control

Abstract

The analysis of time-varying control for robust stabilization and performance improvement is considered. This problem has been investigated in recent years from the point of view of assessing the capabilities of time-varying control to stabilize plants with structured norm bounded perturbations. In this paper, it is shown that time-varying compensation provides no improvement over time-invariant compensation for the stability and performance robustness of discrete-time systems with structured, causal, time-varying, and norm-bounded perturbations, where the norm on the perturbations is the l2 -induced norm. The results of this paper help in completing the picture for the case of time-varying perturbations.