Sector coupling needs consistent communication An interview with Martin Müller of Phoenix Contact on the lack of standards and looking beyond the horizon of the fieldbus world.

Brief summary

From the infamous fieldbus wars to specific Ethernet protocols right through to truly uniform communication based on global standards – that sounds almost too good to be true. Over medium term, can the latest developments truly go somewhere? With communication that no longer really cares about what it is used for in the end? That is to say, one cable for every application. Martin Müller uses the term “convergent networks” for this. In an interview with Thorsten Sienk, the Phoenix Contact veteran in the area of fieldbuses explains why these networks are so important for linking very different sectors.

Interview

Thorsten Sienk:
Interbus, PROFIBUS, CANopen: I can remember a time when there were entire specialist magazines full of all sorts of fieldbus systems. Around the turn of the millennium, it felt that the automation industry was spending more time on developing communication modules than on actual machine functions. They experienced the birth of fieldbuses and also what later became known in the media as the fieldbus wars. So why all of this effort?*

Martin Müller:
What we later called the fieldbus wars really kicked off in the early 1990s. The need for communication between controllers and the sensors and actuators in the field essentially resulted from a tangible source of stress: the parallel wiring of sensors with machine controllers and huge cable harnesses. The development of fieldbuses promised enormous savings and was supported by the state in a so-called joint project. Back then, PROFIBUS, in which Phoenix Contact was involved and what was later closely linked to Siemens, was being specified.

Thorsten Sienk:
In my memory, however, Phoenix Contact was synonymous with INTERBUS.

Martin Müller:
Yes. We were commercially successful with INTERBUS S. S stands for Speed. There was also a C version, which stood for “Communication”, together with Intel and Digital Equipment. At the very beginning, there was also the INTERBUS P as a PROFIBUS spin-off. Ultimately, the INTERBUS S was the only commercial success for Phoenix Contact.

Thorsten Sienk:
Without looking in the rearview mirror too much. Why did the automation industry later decide to bury the classic fieldbuses and use Ethernet instead?

Martin Müller:
The advantage of Ethernet was its ability to transmit more types of different information with one cable. In the past, we had three distinct cables for communication: classic fieldbus, communication for safety technology, and Ethernet for networking intelligent subsystems. Nobody wanted to operate two or three different cables next to each other anymore. This was the start for systems such as CC-Link, EtherCAT®, Powerlink, Sercos3, and also PROFINET.

Thorsten Sienk:
But even here, there was one automation manufacturer behind every name promoting their own system. Would it not have been smarter to take the experience from the coexistence of fieldbuses in order to effectively prevent the uncontrolled growth in protocols? Colleagues from the specialist press were already predicting the second fieldbus war. Individual developments instead of common pacts: had the industry learned nothing?

Martin Müller:
If I look back at the time before the classic fieldbuses, the competition between the various systems was based on the simple fact that there was no standardized communication. There was therefore the need to develop something. This resulted in differentiations between the market competitors. Your question becomes relevant at the latest with the introduction of real time Ethernet – knowing full well that ongoing business depends on these different communication systems for the companies. This applied just as much to the fieldbuses as it does to the Ethernet protocols being further developed.