Observer-based<i>H</i>_∞output tracking control for networked control systems

This paper is concerned with observer-based H ∞ output tracking control for networked control systems. An observer-based controller is implemented through a communication network to drive the output of a controlled plant to track the output of a reference model. The inputs of the controlled plant and the observer-based tracking controller are updated in an asynchronous way because of the effects of network-induced delays and packet dropouts in the controller-to-actuator channel. Taking the asynchronous characteristic into consideration, the resulting closed-loop system is modeled as a system with two interval time-varying delays. A Lyapunov–Krasovskii functional, which makes use of information about the lower and upper bounds of the interval time-varying delays, is constructed to derive a delay-dependent criterion such that the closed-loop system has a desired H ∞ tracking performance. Notice that a separation principle cannot be used to design an observer gain and a control gain due to the asynchronous inputs of the plant and the controller. Instead, a novel design algorithm is proposed by applying a particle swarm optimization technique with the feasibility of the stability criterion to search for the minimum H ∞ tracking performance and the corresponding gains. The effectiveness of the proposed method is illustrated by an example. Copyright © 2013 John Wiley & Sons, Ltd.