I. Introduction
Recently, interconnected systems are used to describe many complex controlled plants, such as computer network systems, multi-machine power systems, and chemical processes [1]–[3]. The traditional centralized control scheme could not satisfy the control requirement of interconnected systems [4]. However, the decentralized control only utilize the subsystem information for feedback control design, which provides a reasonable and feasible control structure for interconnected systems, and it has aroused widespread concern in the past years [5]–[7].