外文翻譯---基于plc和組態(tài)軟件的原油儲罐區(qū)監(jiān)督與控制系統(tǒng)-在線瀏覽
2024-09-24 11:17本頁面
【正文】 ormally munications with the master station of the PLC. If the master system of PLC is in the event of failure, the control job would be taken over by the reserve system, Force Control would disconnect the munication according to the switch flag and turn to the reserve station to exchange dates. B. Hardware Design of PLC System Before selecting PLC modules, analyze the controlled object to count out I/O current requirement and 20% 30% margin should be considered, allowing the system to expand. According to this principle, I/O points are as follows:125 digital inputs,21 analog inputs,84 digital outputs. Based on the analysis of control task, the system chooses Siemens S7300 series of products. This series PLC could Meet requirements of the mediumperformance control system and adopt modular structure. Many different modules can be bined together and users should select appropriate modules according to the actual need. PLC modules selected are shown in Table 1. PLC in the system consists of two S7300 stations each with a CPU 3152DP and two ET200M slave stations. Its structure is shown in Figure 2. The Ethernet munication module CP3431 provides a standard RJ45 interface, one of the functions is to connect the PLC to Industrial Ethernet to municate with puters, and the other function is to provide redundant backup link for master CPU and reserve CPU to realize redundant munication between the two CPUs. Fig. 2 Hardware structure of PLC CPU3152DP provides DP master interface and IM1532 of ET200M provides two DP slave interfaces ,one is connected to the master station and the other to the reserve station through PROFIBUSDP networks. PROFIBUSDP could be Shielded Twisted Pair(RS485) network physically. Normal ET200M consist of a rail, a interface module and some general modules .The modules except power supply are connected through bus connectors. This structure doesn’t support redundantcy functions. There is another configuration that is suitable for redundantcy. It uses a special rail that can take active bus modules and two interface modules. The modules except power supply are mounted on the active bus modules and it is possible to change modules during running. C. Connections of the Electrically Operated Valve Henchun CKD series electric operators are used and Fig. 3 shows its connection method. The feedback of electrically operated valve includes four digital signals and one analog signal. Digital signals are remote mode indicating contact, full open indicating contact, full off indicating contact and mon alarm contact. The analog feedback, a 420mA current, shows the valve’s opening value .When the valve is in the remote control mode, digital outputs of PLC drive the relays and then control the valves. Four output control signals include openvalve signal, closevalve signal, stop signal and emergency protection signal esd. Fig. 3 Valve connection diagram III. SOFTWARE OS THE SYSTEMSoftware in the system includes two major parts, PLC programming software STEP7 and superior puter configuration software Force Control . A. Communication between Superior Computer and PLC Force Control develops a special driver for the S7300 PLC, 2009 3rd International Conference on Power Electronics Systems and Applications Digital Reference: K210509077 therefore it is not necessary for the users to be familiar with the munication protocol between them, and neither necessary to program or configure network in the PLC, the munication between PC and PLC can be achieved easily. The main problem in this system is that due to PLC39。 (3) Drawing graphical interfaces to display the wor
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