Real-time operating environment for networked control systems

This paper discusses the real-time aspects of networked control systems' (NCSs) operating environments. An open-loop unstable magnetic-levitation (Maglev) test bed was constructed and used to develop an NCS with a real-time application interface (RTAI) operating environment. A client-server architecture on a local area network (LAN) was developed with the network communication based on the user datagram protocol (UDP). The implementation of an event-driven server and a time-driven client presented in this paper facilitates a simple timing scheme that does not require clock synchronization between the client and the server. A novel prediction scheme involving the multiple-step-ahead generation of control signals is used to maintain system stability in the presence of excessive time delays and packet losses in the communication network. The current system can compensate for up to 20% data-packet losses without losing stability with the Maglev real-time-control test bed in the communication network.

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