PROFINET Radio – Robust Transmission for Automation

Schildknecht, AG has gained experience with all radio technologies in many thousands of projects since 1993. It is one of the main reasons why we recommended Bluetooth 5.0.  It is the most robust and interference-resistant radio technology. Users see this in high system availability, comparable to that of a cable, with no fieldbus faults. However, Bluetooth alone cannot meet the tough requirements for PROFINET data transmission over the air.  DATAEAGLE has a built-in a pre-processing function that reduces data traffic over the air by about 95% – this is comparable to MP3 for audio. In effect, it is a 1:1 cable replacement for the application and the fieldbus.

Data Reduction Algorithm

Such a replacement is made possible because fieldbuses such as PROFIBUS, PROFINET, and others send cyclic data in millisecond cycles, and the data is usually repeated over multiple cycles. With the right strategy and patented algorithms, the repetitive data is not transmitted over the air, but only the relevant new or changed data. An embedded database in the radio modules can handle a 1ms update time on the cable side providing the positive advantage of keeping a fast application update time.  This is far superior to the alternative of reducing the PROFINET update time to 16, 32 or 64ms, which is today’s preferred data reduction strategy employed in other WLAN solutions. If you set 32ms only new data will be sent in this time. In the worst case this time doubles even after the sampling theorem. Due to the data reduction, DATAEAGLE can transmit changed data after only a few milliseconds. The latency is between 10 and 20ms.

Data reduction algorithms and strategies also meet the very high requirements for fail safe communication such as PROFIsafe. Here, errors in the wireless connection have an even greater impact, as a manual release usually has to be made after a bus or safety error, resulting in very long machine downtimes.

In the 5GANG research project, we used the 5G campus network instead of Bluetooth, which showed that the data reduction strategy can also increase stability and the number of connected wireless professional devices. Part of the research also involved investigating Echoring from the German startup R3, which uses a proprietary MAC layer based on 5Ghz wifi chipsets. Also with Echoring, we were able to see the elimination of bus errors and an improvement in update time.

Foil Cutting Machine

In a foil cutting machine, up to 40 parts are movable with drives, each of which is addressed by the PROFINET controller via a radio link with a PROFINET cycle of 1ms. If a bus error occurs, the result is a machine stop that causes a plant standstill of approximately 15 to 30 minutes and high material loss. By using 40 PROFINET wireless links in one of the machines, there has been no downtime since the end customer switched to the DATAEAGLE 4000 in 2016. Another machine in close proximity to the first machine was outfitted with DATAEAGLE, and since 2018, 80 wireless PROFINET connections have been operating flawlessly in one hall. With this success, all machines in the plant have been equipped with Wireless PROFINET.