On displacement of decentralised fixed modes by discrete time control

Abstract

In this paper we shed light on the uncertainty related to the effects of sampling on the Unstructured Decentralised Fixed Modes (UDFMs) of continuous LTI systems. The uncertainty has arisen due to the fact that for a certain class of LTI systems the UDFMs can be moved by discrete-time controllers while they cannot be moved for others. We identify the reason behind this anomaly and provide the conditions for moving UDFMs in LTI systems by sample-data control. Numerical examples are given to illustrate all aspects of the paper.