This paper is concerned with the robust guaranteed cost control problem for networked control systems (NCSs). The plant considered is an uncertain linear discrete-time system, where the communication limitations include packet-loss and signal transmission delay. Our purpose is to design a robust statefeedback guaranteed cost controller such that the resulting closed-loop system is robustly stable, and a specified quadratic cost function is upper bound for all admissible uncertainties under such communication limitations. A model of NCSs is established which contains two additive delay components, one being a known constant, and the other unknown constant. By introducing a novel Lyapunov-Krasoviskii function with the idea of delay partitioning, new sufficient conditions for the existence of guaranteed cost controllers are proposed. Numerical examples are provided to demonstrate the usefulness of the developed theory. 96 L. WU ET AL. see, for example, [1,[3][4][5][6][7] and references therein. Among these recent results, the stability problem for NCSs has been investigated in [1,8], the stabilization and control problems have been studied in [4,7,9], the H ∞ performance-based control problem has been considered in [6,10].Unlike conventional control systems, in an NCS, the insertion of the communication channels creates discrepancies between the data records to be transmitted and the data records transmitted, and hence, raises new interesting and challenging problems, such as quantization, signal transmission delay, and packet losses. The first issue is the signal transmission delay (sensor-to-controller delay and controller-to-actuator delay), which is usually caused by the limited bit rate of the communication channel, by a node waiting to send out a packet via a busy channel, or by signal processing and propagation. The network-induced delay may degrade the performance of the NCSs and even result in instability. There have been many methodologies available to deal with the signal transmission delay, for example, [7,9]. The other issue raised in NCSs is the packet losses, which are caused by the limited bandwidth and the large amount of data packets transmitted over a single channel [11]. The packet losses are usually unavoidable though many networked systems employ Automatic Repeat reQuest mechanisms. So far, there have been many results reported that deal with the issue of packet losses. For example, Zhang et al. [1] proposed a criterion to check whether the NCS is stable at a certain rate of packet losses, and searched for the maximum packet-loss rate under which the overall system remains stable. Gao et al. [4] considered the packet loss problem and modelled the NCS as a new system with two additive time-varying delay components.In the past few years, there have been growing theoretical interests in the fields of stability analysis, control, filtering, and model reduction of time-delay systems, see, for example, [12][13][14][15][16][17][18][19] and references therein. Although there have been numerous results...
