2N3A3120-D TOSHIBA（用品质传动你我）。 _ 山西润盛进出口有限公司

One or several PLCs and PCs are connected to the system, and the PCs play the role of the original programmer and man-machine interface operation station. This is a new trend in the 1990s, which brings business opportunities for system integration. At the same time, programming software and human Machine interface software (monitoring software or configuration software) and software interface (or driver software) have also been developed.

In recent years, PLC manufacturers have provided the basis of physical layer RS232/422/485 interface on the original CPU template, gradually added various communication interfaces, and provided a complete communication network. Due to the rapid development of data communication technology recently, users have strong requirements for openness, and the fieldbus technology and Ethernet technology are also developing simultaneously, so the PCS system composed of PLC is slightly better than the openness of DCS. At present, Rockwell AB has formed a multi-layer structure system, namely fieldbuses such as Ether Net, Control Net, Device Net and Asi (the original DH+ network is also compatible). In addition to Profibus-DP communication network and Profibus-FMS network, Siemens proposed S7 Routing network, namely Profibus-DP and Industrial Enternet two-layer structure. The network is still developing, and our country should be actively involved in it.

In 2001, my country’s machinery industry became a new bright spot in industrial development. The total output value increased by 17.15% over the previous year. The output of automobiles ranked the top 10 in the world, and the output of machine tools ranked fifth in the world. The profit of machinery industry increased by 33.35%, accounting for more than 60% of the new profit of the whole industry. Exports also showed encouraging growth. At present, the machinery industry proposes to implement networking. PLC practitioners should have a clear understanding of this point, and deal with the openness of networking, the performance/price ratio of network composition, and the reliability, security, and advancement of the network. Work hard.

The upward connection of the network is an Internet problem, and the downward connection is a field bus problem. In addition, whether the existing network can use the Ethernet “e network to the end” method, the network adopts the client/server method, the browser/server method, the producer/consumer The method, the interface software adopts the OPC method and other issues need to be further implemented. PLC and intelligent MCC motor control center, NC/CNC numerical control equipment supporting numerical control machine tools, and other operation control systems, electronic control equipment, frequency converters and soft starters are connected to form a system; PLC should cooperate with DCS division of labor and act as DCS Remote I/O station, etc.; PLC should cooperate with IPC, in addition to using IPC as human-machine interface, it is also feasible to use I/O components of software PLC; in addition, there are PLC and emergency shutdown safety system (ESD, Emergency Shut Down Systems), and three-dimensional warehouses, robots, CAD/CAM, etc. must be handled well. In short, PLC should be compatible with various new technologies, making PLC a “computer” in the true sense.

The application field of PLC is broad, and there are still many fields that need to be developed urgently, such as for customs transit vehicle certification (Shenzhen Yantian), automatic drug sales (several traditional Chinese medicine stores) have examples in my country. In addition, in discrete event systems, such as road network traffic flow (vehicle counting, passenger counting and residence time measurement), logistics systems, flexible manufacturing systems (agile manufacturing systems) and all non-standard service systems, PLC can be used. , and then model and take countermeasures and optimize. The future of PLC is bright, and all pessimistic arguments are untenable. As for technological progress, it will take some time for PLC to merge with other technologies and even disappear!