| With the development of both computer technology and communication technology, the automated system and industry's control system had changed greatly from the system structure, the method of control, product series, the method of man-machine and cooperating, etc. In the 21st century the control system based on network had following main characteristic: on one hand communication and network technology are applied to automation and industrial control deeply, on the other hand management and control of communication network require more adoption in control theory and tactics. Network control and control network is a trend in automation and industrial control in the 21st century. The control system links with enterprise information network Intranet, it is a development trend of a control system to realize management and administration, office automation in enterprises, control dispatchers, real-time control to integrate. The distributed control system (DCS) is that one kind control system which has distribution control, information centralized management characteristic. In general typical DCS includes operation station, control station and communication network. Control station fulfill to distribution control for spot object in real time. Operation station manage computer carries out operation, show, alarm, optimization and control function, etc. Communication network is mutual communication between operation station and control station mainly. Since 1975 American HoneyWell Company put out first collection and distribution control system. HoneyWell Company has presented three generations of DCS products altogether in the more than twenty years later because of technology progress, external environment changing, changing of demand, development of design philosophy. New generation DCS most important characteristic is to make process control, monitor, management modulate combined closely. It has solved the interconnection problem among the equipment of different manufacturers through adopting the open system and standard communication network such as Ethernet and on-the-spot bus, etc. Operation station adopts 32 bits or 64 bits microprocessor and operation station with many functions. It strengthens order control and batch control capability. The system can apply to industrial PC and PLC with much software technology. It has some advance control functions because it adopts the standard figure operating system platform, unifies user's interface, importing the expert system and adaptive process control. There are WINSOCK and COM/DCOM based on TCP/IP network communication technology mainly. WINSOCK is one sets of socket development open and supporting network programming interface of many kinds of Windows of agreement by Berkeley. It is a standard in fact of network programming of Windows. COM (Component Object Model) is a kind of object model on the basis of component that acts as issuance element. The model can make all kinds of software apply each other through union work way. What is called component object defined previously is service or interface that can accomplish certain function in fact. And how these component object coexist with the application program and communicate and mutual each other, this needs to make a norm so that component object can work according to the unified standard way. COM is binary system norm independent of source program. So component object can communicate mutually each other as though they are created through different program language, operated different process room and operation system platform. COM is norm, realization too. It provides standard interface and a group of API functions. Interface has a kind of key function that visit COM object. These API functions are used to create, manage COM object. DCOM is the expansion of COM, it can be said to be a kind of communication protocol, offers the ground floor of communication of component to control, realize to communicate which lies in the different computer COM object each other. These computers can be joined in the LAN, WAN, even through Internet. The combination of TCP/IP network technology and the control technology breed the long-range control network. At present, Intranet of information network based on TCP/IP agreement has already become the mainstream of the information network inside enterprises, Intranet can be connected with external world conveniently, especially connects with Internet, this enables enterprise's staff member to participate in managing various kinds of resources inside enterprises conveniently. That control network is joined Information network Intranet/Internet through the interface of the network makes up of distributed long-range control system. Thus this formed the integratedindustrial corporate network. In this paper, long-range control network is put forward, which mainly includes control network in the spot and long-range control network. Control network adopts the distribution control system based on RS-442 communication protocol to be designed. Long-range control network adopts way of WINDSOCK programming to be realized through operating station inserting TCP/IP network. The communication protocol design of control network spot adopts the multi-layer structure. Physics layer provides physics connection rules and characteristic, which is set up, kept, released mainly among data chain entity. It can realize the binary scale is transmitted between the physics equipment and shield the consolidation difference during implement in order to provide data transmission service for data chain layer. Physics layer of EIA RS-442/485 agreements adopted, have the characteristics that transmit the distance far, with strong anti-interference ability in the communication agreement design of this system, and technology ripe, implement with low costs, convenient to use on a large scale. Data chain layer exploit transmission function that location flow offered by physics layer, carry on reliable transmission of data by frame among the node in communication. Its main function is to provide data chain that is set up, kept, released among the communication entities, service datum element (frame) of transmission layer and realize mistake control and carry on the flow to control etc. The system communication agreement design adopts self-defining frame form and provides functions, which mistake and congest are controlled. The function of using layer is mainly to realize the communication between the control nodes in order to realize the mutual control between the control nodes. Control end software is written finally in this paper. It can divide into some main parts as follows: (1) Initializing setting module The module is responsible for initializing, for instance Potter rate, data location, stopping in the location, odd-even check-up location, overtime, etc. (2) main interface module The module is the interface of human and computer. With the control of the interface we can control the station in the spot or the long-distance. It also can show the state of the window. |
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