Ethernet is probably the most widely used means of communications in the industrial world. There, I said it. This has been a controversial subject for many engineers, and the tide has only recently turned to Ethernet as a de facto standard.
There is always a lot of discussion in the controls community about communications. The speed and reliability of communications systems has always been a weakness in the industrial controls world. The focus has always been on the reliability of the control system execution rather than the control system’s ability to communication with intelligent peripherals. I think everyone viewed it as a great goal to be able to communicate reliably between plant floor control systems with high reliability and enterprise level business systems which are not as critical at a millisecond by millisecond framework. Ethernet communications has been more than capable to meet the early needs of industry.
But typical of most industrial control users, anything that was used in the office was viewed with great suspicion by the plant floor engineers. After all, if beverage lines are running at 1,000,000 units a day, missing data communications within the control system can throw a big wrench in manufacturing. Also common for industrial users is the complaint about ruggedness and reliability. No one serious wants to trust their industrial processes to a little RJ45 connector.
Industrial controls manufacturers responded with their individual networks that were engineered to perform at the highest speeds possible with the greatest reliability possible. Modbus, CAN bus, DeviceNet, ControlNet, ASI, Hart, Sercos, Firewire and many other communications technologies were developed and used to add very important functionality to the controls arena. Commonly, large controls manufacturers sought to introduce their proprietary communications hardware and software protocols in an effort to gains some advantage in the marketplace.
It’s hard to argue with a solution that you can buy at the local Radio Shack. Pick up a connector, wire and crimping tool for next to nothing and go to town. Low cost and high availability. If there was a concern about mechanical reliability, there are many suppliers like Turck and others making IP67 washdown rated protection for the physical connectors themselves.
The biggest issue facing Ethernet in the past was bandwidth, which has progressed exponentionally from megabaud to gigabaud rates. Speed alone is not a guarantee of delivery. Determinism in the network requires additional overhead that Ethernet never provided for. To meet the need for determinism several approaches have been tried with the clear winner being EtherCat from Beckhoff. National Instruments, Yaskawa, Kollmorgen and many other companies are now making EtherCat compatible products, simplifying the problem of network integration and application reliability for industrial plant users and OEMs building machinery with EtherCat as an internal network.