Bridging the gap: Profinet for Process Automation

01 September 2006

After safety, factory automation, and drives and motion control, Profibus International is now ready to make Profinet available for process automation.

'Protecting existing investment in skills and equipment is our highest priority in adapting our Ethernet-based Profinet technology to process automation. That is the most important message for our end users and
manufacturers. The long life times of installations in process technology prevent us from introducing a paradigm shift every few years,’ stresses Edgar Küster, Chairman of Profibus International (PI).

The central topic ‘Profinet for Process Automation’ was first addressed at a PI advisory board meeting in March 2006. PI aims to finish the specification for connecting Profibus PA and HART devices by the end of 2006; Fieldbus Foundation connectivity will be addressed in 2007. Profinet systems with comprehensive system capacities for process automation are expected in 2008 and 2009.

Initially, only Profibus DP will be replaced by Profinet. Already installed process instruments can be used in the Profinet world. The Profibus PA, HART and Fieldbus Foundation networks remain as they are.

Profinet for factory automation The Profinet project for factory automation has been largely completed in terms of PI. The goal is that all profiles defined with Profibus will continue under Profinet. This is already working for PROFIdrive applications. PROFIsafe for Profinet is likewise finished and initial applications are already in the automobile industry. The four German automobile manufacturers that sail under the common AIDA flag (Automation Initiative of German Automobile Manufacturers) Audi, BMW, DaimlerChrysler and VW are familiar with Profinet with the PROFIsafe profile and have specified an aggressive schedule to component manufacturers.

The four AIDA auto makers want to integrate PROFIsafe in their new systems within the next year because integrating safety technology into control technology offers a high potential for benefit. The consolidation significantly reduces the effort in planning, implementation and operation, which helps the automobile industry cope with the high pressure of costs.

Big challenge
The big challenge when employing fieldbuses and industrial Ethernet together lies in the exchange of data
between the two worlds, because the data structures are entirely different. It makes no difference, incidentally, which fieldbus system is involved.

Until now, this has meant that individual solutions had been required for communication from top (the IT
level) to bottom (the field level). ‘With Profinet IO, we address remote I/O at the field level with Ethernet, making data exchange between field and company-wide IT levels much easier because everything is based on TCP/IP,’ says Mr. Küster.

This continuity also has other advantages. Transparent pass-through to field devices is particularly apparent
during diagnostics and commissioning. In a typical fieldbus system, the PLC or control system is the central system that moves information from the field level to the IT level. With Profinet the user has access to the data from a motor starter or, in the near future, to a pressure transmitter and to HART devices from any engineering system. Today, Profibus PA devices are integrated by means of a PA coupler or a PA linking device in Profibus DP (Fig 2). Soon they will simply be connected by means of proxy technology on Profinet.

When employed in process automation, the existing core functions of Profinet IO remain unchanged and
include additional benefits. An important aspect here is the integration of the DCS systems in the company-wide information systems (MES) and asset management systems.

The PI Working Group ‘DCS Requirements’ headed by Bernd Wansner of ABB and Björn Moeller of
Siemens is addressing the central topic of PA. The working group is, for example, attending to questions of configuration and engineering, as well as system requirements such as system redundancy, time stamping, and time synchronisation.

The adaptation of PA device profiles and other PA application profiles to the enhanced features of Ethernet is at the top of the list. Overall, there are a number of individual topics to clarify and specify, although a number of solutions can be taken from production automation or ‘just’ need to be adapted. For example, media redundancy is today considered resolved. The topic of system redundancy—very well established in
the DCS world—is outstanding.

The PROFIsafe and data security functions are being examined to determine whether they can also be
integrated seamlessly in Profinet for Process Automation. ‘We just have to see what still has to be done on the PROFIsafe profile so that it similarly fits for Profibus PA and Profinet. It is largely complete, but we want to be sure that we have not overlooked anything,’ explains Mr. Küster.

PI is working very closely with NAMUR, ZVEI and GMA in this area. PA products with PROFIsafe profile will be
coming on the market this year. Profinet should be available by the end of 2008 for all areas of application in
automation. Experts are assembling the ‘technology puzzle’ piece by piece (Fig. 4).

Some examples
In practice, Profinet is already used in process automation without much attention, primarily in industries with ‘hybrid’ applications, such as bottling, packaging, transport and logistics, and energy management. These are found in the cosmetics, pharmaceutical, and food and beverage industries. Production and process automation increasingly intermix, in idea and in implementation.

Connecting PA devices on Profinet in these applications currently requires two steps, via a normal Profibus DP proxy and a PA link or PA coupler. This is somewhat circuitous, but it works! A considerably more cost-effective PA proxy will soon take care of both device functions in a single product.

All of today’s installations of this ‘double bridge’ approach (from PA to DP and then to Profinet) function
flawlessly. A prime application is with Peterstaler Mineralbrunnen in the Black Forest. The renowned bottler linked its production plants in Peterstal andRippoldsau, which are separated by 14 kilometres through a mountain range, using a ‘mineral water pipeline.’

On this project, Klotter Elektrotechnik implemented a solution that runs from the flow control and pressure regulation via the pressure monitoring and fill level measurement to the management of tank control via Profinet in real-time. Through the Ethernet backbone, the company is able to enjoy extra benefits such as Voice over IP telephony. Not to be overlooked is the fact that Profinet I/O can be configured similar to the
Profibus DP structures. The system provider used all the technical features of Profinet at Peterstaler
Mineralbrunnen. Data from typical process devices such as pressure, fill level, ane flow rate are also transmitted by Profinet.

Yet another company in the Black Forest is leading the way technologically. Profinet monitors energy consumption for Pappenfabrik A. Köhler in Gengenbach. The existing Ethernet infrastructure was used for
implementation and Profinet easily and cost-effectively combined with existing Profibus segments.

Further to the south in sunny Spain, Maval Instalaciones y Automatización automated the bakeries of the leading regional supermarket chain Mercadona. The bread production lines for 881 markets are now globally integrated by means of Profinet components. What reasons did the customer give for Profinet? There are three of them: 1) A uniform communication standard; 2) It facilitates the horizontal and vertical
flow of data and provides openness for TCP/IP; and 3) The technology increases data transfer rates.

These are just three examples that show Profinet is working seamlessly in hybrid applications. After finalising all functions, the goal is to ‘kick start’ Profinet in all other branches of process automation.

‘We view the PNO as the only technology driver that can tackle this complex task today and want to prove
this with clear goals and dates. Just as we have implemented Profinet for production automation and have solved the extremely demanding topic of motion control, we will crack process automation,’ says Mr. Küster with confidence. ‘Of course, there’s still some work to do, but that’s our job.’

Author: Dr. Volker Oestreich; Executive Director, Profibus International


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