| Ethernet Technology in Industrial Control Applications |
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| Written by AIA |
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To automate your plant effectively, you need to network everything - from the simplest device all the way to the Internet. And, if your plant is like the most, you already have a number of networks installed for different purposes. But with a wide range of devices, networks and protocols you will likely have trouble getting all your system to speak the same language. This affects your productivity, increases your costs and limits your ability to react to change quickly. EtherNet/IP, together with the ControlNet and DeviceNet (Open networks), allows sharing of data between different applications with ease. No extra hardware or additional programming is required. With this, remote customer order entry to manufacturing to product delivery becomes a reality. The network helps to communicate information seamlessly throughout the plant, from shop-floor to top-floor, and to and from the Internet for e-business applications. Ethernet technology has been used since the mid 70s and is widely accepted throughout the world, consequently it stands that Ethernet delivers the largest community of vendors in the world. The high demand for Ethernet-compatible control applications drove the design and creation of EtherNet/ IP. EtherNet/IP is an open network that uses existing commercial technology, including: - IEEE802.3 Physical and DataLink Standard - Ethernet Transmission Protocol Internet (TCP/IP) protocol suite, the Ethernet Industry Standard - Common Industrial Protocol (CIP) TCP/IP is the transport and network layer protocol of the Internet and is commonly linked with Ethernet Installations and the business world. To make EtherNet/ IP successful, CIP has been added to provide a common application layer. EtherNet/ IP uses the producer or consumer network model as do Device Net and ControlNet networks, which also use CIP. EtherNet/ IP is designed to handle large amounts of messaging data up to 1500 bytes per packet. In addition to data handling, EtherNet/IP's speed, 10/100 Mbps, makes data transmission even more appealing. A common strategy of using open networking technology for seamless, top-floor to shop-floor integration is through Open Network Architecture. The architecture provides the ability to control, configure and collect data on a single network, thus simplifying the plant communications. The complete EtherNet /IP solutions follow the - Device Level, which allows users to reduce hardwiring, save installation time and costs, and gain valuable diagnostics from various sensors, actuators and other devices connecting to the control system. - Control Level, which provides deterministic, repeatable performance for I/O, programming and peer-to-peer communication and data collection while spanning the entire manufacturing process from raw materials to finished products.- Enterprise Level, which allows various MES and Data Archiving systems access to plant floor data for financial, quality, manufacturing and development purposes. Ethernet IP provides easy and reliable solutions at Cadbury Cadbury's 'Crunchie' is one of the top selling chocolate bars in the United Kingdom. While the plant used for producing the Crunchie Bar is modern, the existing control system, installed in 1981 was becoming a problem. Over 1 million bars can be produced each day at a rate of 1200 bars per minute. The honeycombed centre is mixed to produce high temperature foam. The foam is then fed onto a moving conveyor where it ismonitored to maintain a constant thickness. Ethernet / IP provided the backbone for all communications between PLCs and PCs running the SCADA software package. The SCADA allowed monitoring and controlling of automated machines and processes. With its rich graphics and enhanced tools an accurate representation of the large complex Crunchie line could be sent to operators in a remote Control room. NB: *Control Net is a Control Level open network maintained by an independent body called ControlNet International. * DeviceNet is a device level open network maintained by an independent body called ODVA * EtherNet/ IP is an information level Open - Debashish Ghosh
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