University of Twente Student Theses


Real-Time Network for Distributed Control

Zhang, Yuchen (2005) Real-Time Network for Distributed Control.

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Abstract:Nowadays, complex control systems, e.g. for industrial automation, are evolving from centralized architectures to distributed architectures. To design a distributed control system, a critical issue is to lay out a hard real-time communication infrastructure. To this end, two kinds of solutions can be categorized from contemporary approaches: the hardware-based solution and the software-based solution. Compared with the hardware-based solution, the software-based solution is generally more cost-effective, adaptable and extendable. Therefore it is more widely applied, especially in laboratory. FireWire is a high performance serial bus for connecting heterogeneous devices. Though firstly targeted for consumer-electronic applications, many of FireWire's features make it well fit in industrial and laboratorial context. In this MSc assignment, following the general principles of the software-based solution, the Real-Time FireWire Subsystem (RT-FireWire) in Linux/RTAI has been designed and implemented. RT-FireWire provides a customizable and extensible framework for hard real-time communication over FireWire. Via performance benchmarking, it has been shown that the transaction latency on RT-FireWire is limited to a certain range that is usable for distributed control applications, whether the system is under heavy load or not. Ethernet Emulation over FireWire (Eth1394) has been implemented on RT-FireWire as a highlevel module in the application layer. Via Eth1394, RT-FireWire can be connected to another real-time software framework RTnet, which implements real-time networking on the IP layer. Therefore, FireWire has been introduced as a new medium alternative to Ethernet for real-time IP networking. The benchmarking on Eth1394 and Ethernet shows that the real-time performance of both is comparable. The real-time networking support provided by RT-FireWire has been integrated to a toolchain for controller design and verification. The toolchain is developed at Control Engineering Group of University of Twente. By using this toolchain with the newly added networking support, a controller that has been designed and verified in simulation can now be easily deployed into multiple nodes. For demonstration, a simple but real-life distributed control system has been built by using this toolchain and FireWire. The measurement results on that system proofs that, FireWire, with RT-FireWire steering on it, can be used as a fieldbus for a distributed control application. The development on RT-FireWire can be continued in several irections: a new interface can be developed to directly operate on RT-FireWire layer; new middleware application protocols (e.g. CANopen) can be investigated to see if they can be stacked on the basic real-time services provided by RT-FireWire; real-time vision control over FireWire is another interesting topic that has not been fully opened.
Item Type:Essay (Master)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:53 electrotechnology
Programme:Electrical Engineering MSc (60353)
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