PROFINET: Highest availability requires tailor-made validation
PROFINET is enjoying growing popularity: As an open standard, the Industrial Ethernet-based fieldbus enables manufacturer-independent automation solutions that can be used in all areas of the manufacturing and process industries. Taking full advantage of the potential of PROFINET applications requires individually tailored procedures when commissioning new and expanded systems.
PROFIBUS, DeviceNet or Modbus RTU: Fieldbuses with serial protocols based on RS-485 have long been the backbone of automation technology. Serial bus systems are reliable, resilient and flexible, and commissioning is relatively straightforward in that the quality of the cable installation and the signal quality can be easily checked by appropriate measurements. While serial bus systems will continue to play an important role in the future, solutions based on Industrial Ethernet, which require a completely different approach during commissioning, are becoming increasingly common with regard to Industry 4.0 applications. The focus is less on cable measurements, signal levels or signal shapes, but in the case of standards such as PROFINET, optimum utilization and the greatest possible availability of the networks are the focus of interest.
Open standard, different protocols
The advantage of open and vendor-independent networks is sometimes the disadvantage that many different transmission protocols have to come together and be reconciled. The commissioning of PROFINET networks focuses less on the physical transmission layer of the cable installation than on the diagnosis of transmission protocols in order to precisely evaluate the function of the individual components and adjust them if necessary. "Very often, operators of PROFINET installations do not have the necessary experience to detect and correct weaknesses at the protocol level," says Bernd Kremer, Managing Director of Aunex GmbH. "Each installation has its own peculiarities, and only the practical work on numerous projects from various industries ultimately leads to the knowledge of what needs to be considered in detail." Kremer gives an example: "The update rate for PROFINET communication automatically assigned in engineering tools is usually set unnecessarily high. Often the application does not necessarily require this. In this case for example, readjusting the update rate can significantly reduce the cyclic network load and hence improve the communication performance and network stability."
Control and use the data flow in a targeted manner
On the other hand, the wish of many plant operators to gain and analyze more and more data from a network with regard to Industry 4.0 applications can often lead to network load problems and high error rates. Aunex therefore recommends using only "managed switches" in PROFINET installations. These have their own IP address and provide information, for example status, error rate and network load of their ports, thus enabling targeted monitoring of data flow in the network and efficient use of existing resources.
Also the functional test of the installed connection cables becomes easier with the use of managed switches. The error rates at the individual ports quickly reveal physical problems. Bernd Kremer: "If e.g. the wiring causes problems with data transmission, the CRC error rate on the affected port increases, and a defective cable connection can then be targeted and quickly located. "
When validating PROFINET installations, Aunex uses the available tools of several manufacturers in order to achieve the best system-specific results. So the time and cost required for acceptances and commissioning is kept as low as possible.