When a cold front approaches hot, settled air, one can expect a great deal of turbulence, lightning and maybe a tornado or two. This is how Ethernet could be viewed as it moves onto the plant floor, with information technologists and control engineers struggling to find a balance. As industrial Ethernet is deployed, there is an evolution taking place that will eventually lead to a calmer atmosphere.
Early applications of Ethernet were isolated to having only certain plant floor computers connected to the network. The limited number of factory connections and the concern for network security required that these connections be managed by the Information Technology (IT) department. This was easily handled as each connection was directly brought back to the IT closet.
Today, Ethernet-connected devices are increasing to include electrical equipment such as programmable controllers, motor control centers and even input/output devices in some applications. The connections, including Ethernet switches, are being installed in the electrical enclosures that are distributed throughout the plant or located in remote areas. Recognizing this trend, commercial supplier Cisco (www.cisco.com) redesigned a standard 19-in. rack-mounted switch into a DIN rail-mounted industrial switch. With Ethernet equipment mounted in these electrical enclosures, local technicians will need to provide some level of support.
Traffic patterns
In an office environment, 80 percent of the devices act as clients requesting information. These are the personal computers that sit on every desk requesting information from larger server computers or databases. On the plant floor, 80 percent of the devices are serving information via User Datagram Protocol or Multicast methods, in which data is continuously sent in small packets, transmitted to devices subscribing to the source. This is the heart of the EtherNet/Internet Protocol implicit messaging structure.
In addition, traditional Transmission Control Protocol/Internet Protocol messages are sent between devices. Local grouping or subnets and the ability of managed switches or routers to isolate traffic will be necessary to ensure correct operation and avoid collision domains. A key collaboration between engineering and IT is required, since the controls group understands the requirements of the processes and timing, while IT can provide valuable support in network architectures.
The use of network management can also be divided into two primary areas of concern. The main focus for the control engineers is to keep the network running, while security and enterprise server availability are the major interests of IT. Only recently have tools been developed that provide the controls group with a focused solution targeted at connections or end devices.
Roughly 90 percent of all plant floor problems are caused by a connection failure of a specific device or, even more difficult to find, intermittent failures brought on by the hostile manufacturing environment. Specialized software, such as IntraVUE from Industrial Communication Technologies (www.ictglobal.com), provides a tool oriented to plant floor uptime activities. These software packages provide visualization of network activities including devices added and removed and intermittent losses in communications. This allows the IT department to remotely monitor the network without having to physically travel to the distributed device. And it allows the local technician to view a problem on the network.
There is no doubt that the use of Ethernet will continue to expand. Developing a network strategy coordinated by both the IT and controls departments will keep the company in bright sunshine.
Mark Fondl, [email protected], is president of Network Vision, an industrial networking systems integrator and network product supplier.
