Quo Vadis Industrial Ethernet?
Industrial Ethernet is coming slowly, but massively.
The industry is waiting eagerly for the ability to use Ethernet safely in automation and process control.
In some areas, Ethernet does have clear advantages. On one hand, presently there is still a more or less strict separation of office and production, and on the other hand, decreasing prices for hardware are expected (e.g. cables and modules) when an "Industrial Ethernet" is available, which is suitable for mass production. In addition, the demand for bandwidth is increasing steadily even in automation engineering, and in the near future this will lead to fieldbuses reaching their limits.
The vision is clear – universal, broadband communication solutions from the machine up to CE level. In the area of internal networking down to control level (SPS/PC) of production, Ethernet is already standard practice, but the last step down to I/O level still is missing.
Until recently, the requirements for the real-time behavior in automation engineering were a technological as well as an emotional limit for practical use.
What use is the information of a sensor when it is already obsolete when it arrives at the control?
Fieldbuses solve this problem by overwriting the last value in a buffer. The Ethernet delivers all values one after the other - but how do the controls know which value is correct? The Ethernet world is a client-server world. Only two partners communicate with each other one after the other, and a printer for example responds and processes everything in series. Fieldbuses talk to each other simultaneously, and this is an immense advantage in the real-time behavior. Fieldbuses are also safer with regard to crosstalk and electromagnetic contamination. A further disadvantage of the Ethernet is the unfavorable star topology, which means additional cable and wiring expenditure.
However, the strengths of Ethernet/TCP/IP are in monitoring and configuration entire installations and the consistency with the in-house Intranet. The Ethernet also has a great advantage with regard to redundancy and plug & play in operation.
For this reason, until now both systems exist in a kind of parallel world.
By now, however, a serial fieldbus based on Ethernet exists with EtherCAT and EthernetIP. The open protocol is suited for hard and soft real-time requirements in the automation technology. Development was focused on extremely short cycle times (= 100 µs), low jitter for exact synchronization (= 1 µs), and low hardware costs. Thus Industrial Ethernet will come; it is only a question of time and at what speed. The good old fieldbus has not yet outlived its usefulness, but it will slowly have to say goodbye to its large niche in exchange for a smaller one.
And those companies having to process large quantities of process data or where the cost advantages outweigh the disadvantages probably will make the first step. The convenient side effect of "Manufacturing data to Intranet" will be a nice by-product.
2010 A.Mueller
