Introduction

Abstract

In the control literature, a system consisting of several interconnected subsystems (which may be geographically distributed) is referred to as a large-scale system. In this type of system, it is often desired to perform the control function in a decentralized fashion. In fact, for such systems it is not realistic to assume that all output measurements can be transmitted to every local control station. Problems of this kind appear for example in electric power systems, communication networks, large space structures, robotic systems, economic systems and traffic networks, to name only a few. Typical large-scale control systems have several local control stations, which observe only local outputs and control only local inputs. Every local controller is involved, however, in the operation of the overall system.