Development Of PLC Control System Of Automobile Manufacture Line And Integrating It With DCS

In 60's, automation control system of auto manufacture line mainly was constituted by relays. The system of relays need to be redesigned and reinstalled when developing a new type automobile. With the development of the auto manufacture, the cycle of redesign automobile was became more and more short, so the system of relays need to be redesigned and reinstalled regularly; in the same time, changing relays system means a long time of fussy work and expensive, farther more that block the periodically renovation of product. For this reason, DEC manufacture the first a set of PLC (programmable logic controller) that was used successfully in GM's automation, assemble line in 1969.Distributed control system was developed basis on computer technology, control technology and network technology. In the middle of 70's, the analog instrument control system take it place for DCS which occurred mainly for analog control purpose. Distributed control system normally use several controllers control all nodes in process of produce. Each controller use network exchanging data and information. Control station read correlative product data and convey operating command through network by connect controller. So DCS can be defined as "distributed control, centralized manage".PLC and DCS have their owner obvious strongpoint and shortcoming. For example, PLC specialize in high-speed control in sequence logic control, and DCS specialize in complex process control. PLC is easy to use and has more little cubage and lower price than DCS; accordingly DCS is good at communication and management than PLC, but in the same time that means more expensive.With the development of electric technology and network technology, modern industry control technology, PLC and DCS application develop more quick and now become two kinds main control technology using in industry control field thought they technology origin, research aim and application field are different.The paper research content include two aspect:1, Study the method of designing automobile PLC welding control system, develop PLC program about convey table and design HMI program, analyze itscommunication network structure and configurate it.2, According to status of automation control system used in auto plant and PLC's application, DCS's application state, supply a scheme of information integration about PLC and DCS based on Modbus protocol. Under requirement of client, this mix control system achieves successfully information exchange between PLC and DCS through communication serial port.The mainly work content about this paper as follow:1, Narrate and analyze PLC's origin, basic characteristic and concept, network communication structure and communication protocol of mainstream manufacture.2, Narrate and analyze DCS's framework and function module. Combining its distribute technology analyze data communication and network structure.3, Analyze the method of designing automobile PLC welding control system, how to develop PLC program about single device unit and design HMI program, analyze its communication network structure and configurate it.4, Compare technology of PLC and DCS and analyze feasibility about its integration. Supply a scheme for PLC and DCS integration based on protocol and how to realize it in product system of auto industry.