Model-dependent Scheduling and H-infinity Control Co-design for Networked Control Systems
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ISSN:1598-6446 eISSN:2005-4092 http://www.springer.com/12555
Model-dependent Scheduling and H-infinity Control Co-design for Networked Control Systems Shunli Zhao* and Yuehui Ji Abstract: In this paper, a novel model-dependent scheduling scheme is proposed for the networked control systems with time-delay, disturbance, and medium access constraints. The scheduler calculates the error between the ideal dynamic and the real system, and selects the states that make the stability of the system better to access the network. In addition, two kinds of representative time-delays in the networked control systems, constant time-delay and random time-delay, are considered. A robust H-infinity and switched-system-based co-design strategy is introduced to deal with the disturbance in the system, and the system uncertainty introduced by the random time-delay as well. Finally, illustrative examples are given to demonstrate the effectivity of the proposed scheduling method and the co-design scheme. Keywords: Co-design, medium access constraint, model-dependent scheduling, switched system.
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INTRODUCTION
Networked control systems (NCSs) has attracted much attention in the past few years [1–3]. Different from traditional control systems, elements like controllers, sensors and actuators in NCSs are integrated with each other via a network. This architecture obviously has many advantages, such as easy wiring and maintenance. However, there are also several challenges introduced by the network in the analysis and design of NCSs, for example, time-delay because of the information transmission [4–6], packet dropout [7–10], saturation [11–13] and disorder [14], and so on. In NCSs, there are two kinds of mediums used to transmit information, i.e., wired network and wireless network. However, the bandwidth resourse is a critical consideration not only for the wire network but also for the wireless network. How to effectively allocate or reduce the use of the limit bandwidth resource is of great importance. In order to reduce the use of the bandwidth, a new scheme called event-triggered mechanism [15–18], is proposed. Compared with the traditional uniform sampling method, event-triggered method is a demand-oriented sampling strategy. Namely, the states are transmitted when they satisfy some event-triggered conditions.
Another problem about bandwidth limitation is called the medium access constraint where only parts of the states can access the network at a sampling instant [19]. Which of the states can gain the access to the network will be dependent on the priority-based scheduling scheme [20–22], derived from the CPU task scheduling [23–25]. Later, communication-sequence-based scheduling method is proposed in [26]. In this scheme, the sates can be separately scheduled as the states and the communication sequence are one to one correspondence. In addition, the scheduling scheme and the control scheme can be designed together, such as periodic communication-sequence-based scheduling and control co-design [27] and the non-periodic commu
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