The original motivation to investigate interconnected systems and decentralized controllers resulted from the impossibility to connect geographically distributed systems by reliable communication links three decades ago. Energy or water distribution networks have been studied to answer the question: Which control tasks can be accomplished by a set of local feedback controllers where each control station has access only to the inputs and the outputs of the associated subsystem.

The revival of interest in large-scale systems in the recent years came with the availability of modern digital communication networks. The question is now: Which information links are necessary to ensure a satisfactory performance of the overall system. The result on decentralized control can help to answer this question by showing the capabilities and the limit of feedback structures that have to satisfy structural constraints.

This reprint of a monograph gives a survey of the analysis methods of large-scale systems and the design methods for decentralized controllers, which can be used as a starting point for the investigation of networked control systems.