Communications Mechanism In Distributed Control Systems

Distributed System can be seen everywhere, and distributed control system is an important research topic in control domain. Problem solving in distributed system usually is to decompose a large system in several smaller parts, then distribute system's mission to them. Finally together with interface technology, communication technology and control theory, an inspecting, controlling and decision-making system is composed in layers.Communication and coordination is the key technology in a distributed control system. Communication which is the nerve center of distributed control system, links all distributed subsystems, and realizes coordination and share of system resource. This thesis is organized as follows:1. In the first chapter, history and actual state of distributed control system is briefly described. Then the communication technology of distribution system, including wireless communication and Filedbus in industrial control system, is discussed in detail. The importance of wireless communication and filefish in industrial control system is pointed out. All problems which this thesis will discuss, study and solve are listed in order to help readers to understand.2. Fieldbus is introduced, and several Fieldbus protocols is compared in order to know more knowledge about Fieldbus. We select to apply Profibus to a paper-product line. The device for the paper-product line is introduced in detail, then the detailed design of paper-product line is given. In addition, how to design the Profibus Fieldbus system in the paper-product line is discussed in detail. Tension is important in paper control system. A virtual tension control system is designed to enhance the performance of paper-product line.3. The performance of protocol applied to wireless communication is the focus of this thesis. Through analysis and simulations, the comparison of the performances and characteristics of Token-Ring protocol and "free competition" protocol is given.Then Token-Ring protocol as the better protocol applied to wireless communication of single-vehicle pressure-testing system is chosen from the mentioned two protocols.4. Wireless communication is applied in a distributed single-vehicle pressure-testing system (SVPTS). We describe the wireless communication network in detail including system structure, self-organization technology and application of Token ring. Then we give out the flow of SVPTS as well as the software. The application and sample of SVPTS in Huaihua is presented.5. In the last part of this thesis, we summarize our works, and the problem still lied in the wireless communication and Fieldbus system is listed to remind readers who are interesting in these two domain.