Source: Magazine "INDUSTRIE ANZEIGER" Nr. 8/9 2004 - Author: Werner Möller ia-redaktion@t-online.de

Plug-and-Play-Solution by standardised bus-profiles

Unitary network utilises the power of each device

For the machine manufacturers the offered definitions of device profiles at industrial bus systems are not sufficient. As they don’t want to follow up with details they desire independent application profiles. With CANopen they make a find as been obvious on a VDMA-meeting in Frankfurt/M. (Germany)

In IT the most common communication system is by far the Ethernet which takes its place more and more in the industrial environment. The reason for that is that the world of automation wants to use the advantages of the IT-world – particular the consistency of the system by unitary independent profiles. For the linking on the field level or in single machines and installations are the same conditions applying. Only such the units and components of different make you can become linked without larger detailed knowledge.

On this way for the field busses CANopen, Devicenet, Interbus, or Profibus bus-system specific profiles became already developed. That means that inside of a system the units can communicate with each other by the single busses. But many users feel restricted because they only can revert to the product range carried by some companies. The next step to more frankness logically would be bus-independent profiles. But the so far only independent application profile was published by the VDMA Frankfurt in the professional association “Fluidtechnik für Hydraulikgeräte”. Only this represents a progressing standardisation of communication.

So Peter Früauf of VDMA-professional association „Industrial Communication“ was promting / urging the machine- and system manufacturers to take part in the standardisation of unit-, interface-, and application-profiles. He made clear that only user-know how a practice-oriented specification can define it.

“Desirable are bus system- and network-independent profiles to enable a most simple paradigm shift” says Früauf. First basic approaches are already there. “Some of the bus syndicates as EthercatTechnology Group, Ethernet Powerlink Standardization Group or 1394-Automation have announced to adapt the CANopen-profile family” explained Holger Zellwanger, board member of the international User- and Fabricators-Union Can in Automation (CiA). Because with the basic approach of CANopen, for years a largely open solution is in the market. Represented by CiA quite a number of mostly medium-sized enterprises is working on application profiles.

One example is the application profile for Extruder-succession units. It was defined by CiA in cooperation with the European Euromap-Organisation (VDMA). The VDMA took this as an occasion to organise the meeting “CANopen profiles – applications for machine-building” at the beginning of the year. More than 60 participants were discussing the state of standardisation. Machine-builders were present who presented application profiles from the fields of waste-collecting vehicles, passengers- and cargo-lifts, extruder systems, printing machines, as well as hydraulic systems.

The majority of the speakers made clear that in these days more and more the demand is a plug-and-play ability, as the system integrators don’t want to deal with the details of communication. They positively pointed out to the task forces which generated the profiles quick and unbureaucratically, to which the moderation and editing work of the CiA-staff members has crucially contributed. A result of the cooperation of fabricators and users in defining CANopen profiles is the model of waste-collecting vehicle.

Andreas Schmidt from Moba:
The at time unique independent fieldbus-profile for hydraulic units was published by VDMA. Only this represents a processing standardisation of the communication
(Picture: Bosch Rexroth)

Mobile Automation GmbH in Dresden/Germany developed the profile with the name Clean-Open (CiA 422) for waste-collecting vehicles. The complete controller system for “waste-cars”, basing on a concept of virtual units is also supported by the “Bund Deutscher Entsorger” (BDE). That this really works in practice was live to see for the visitors of Entsorga in Köln/Germany in autumn 2003. The application profile was meant to be published in this spring and then submitted to the international standardisation. From the field of lift-controllers Jörg Hellmich from Böhnke + Partner GmbH presented the application profile for lift-controllers (CiA 417). The enterprise from Bergisch Gladbach/Germany exhibited on the “Interlift 2003” trade fair in Augsburg/Germany first prototype installations. This open lift-profile was supported in large extend by the middle sized lift-industry.

Peter Früauf vom VDMA-Fachverband Industriell Communi-cation (Picture: VDMA):
"The Machine- and System-builders must active participate in the Standardisation”

The four-part specification supports the description of eight controllers for up to 127 landings. In total can be netted multi-thousand virtual units in one system. As in a physically CANopen-network only max 127 units can be supported the controller maker have installed transparent gateways. As a single drop of bitterness Jörg Hellmich mentions the little acceptance from the drive-producers. “They are the only who did not yet translate the profile into action. But with some effort of configuration we can integrate CANopen-drives on CiA 402 to our lift-systems” the lift-specialist says.

Unit-profiles for sheet offset printing machines developed by a private consortium of companies, was presented by Edgar Sauer from Heidelberger Druckmaschinen AG. Great importance was attached in the definition that make-specific features are recordable / describable. So the profiles deliver a frame which is still to fill by the printing machine manufacturers in cooperation with the sub-system suppliers. The control station operation of the peripheral equipment is one of the most important.

CiA-Vorstandsmitglied Holger Zeltwanger (Picture: CiA):
"Some Bus-consortiums as Ethercat Technology Group, will adopt Can-Open-Profile"

Advantages. “Also the multi-use of data and a cross-communication between the peripheral equipment are important functions which can be realised by CANopen”, Sauer reported. Peter Hammer from Vienna developed profiles for Extruder-succession units (CiA420). “More than the half of the Extruder-manufacturers will support this standard” emphasised the assistant of Cincinnati Extrusion GmbH. User and maker have managed it to build up a first reference plants within less than half a year.

In the workshop at least two of the equipment producers were involved. This not only underwrote a high acceptance but also a high versatile technical competence. CANopen implementations of the bus-system-independent VDMA-equipment profile for "Fluid PowerTechnology" is the special subject of Alexander Meißelbach. The assistant of Bosch Rexroth AG from Lohr/Germany reported about the backgrounds of developing the profile: “Our main competition actually is the electrical drive-technique, and as they already had standardised equipment profiles for different bus-systems we were in a tight spot”. The translation to CANopen became realized in an own CiA-document (CiA-408) and describes simple valves as well as complex hydraulic governors. „With this components we have achieved an equal status of hydraulic and electrical drives regarding the function, interface, and operation”, said Meißelbach.

The communication in safety-relevant in critical applications was the topic of Heinz Gall. The assistant of TÜV Rheinland Berlin Brandenburg Anlagentechnik GmbH in Cologne/Germany was dealing with the demands of communication systems in standardisation and testing regulations.

All standardisations for safety-relevant

Standard-Interfaces
and Application profiles
must become developed

Machines and systems are basing on the basic standardisation IEC 61508. Also the latest standardisation EN 954 (also see page 24) will be revised in this direction. For CANopen applications there is a safety-protocol (CiA 304) with that you can obtain the safety-level (SIL) 3 as to IEC 61508. The TÜV-assistant mentioned that in the new EN-standardisation 954 additional performance level become defined which are to be considered. Under guidance of CiA a consortium of companies at time is implementing the safety-protocol in a 16-bit micro controller for to become exemplified by the TÜV-Rheinland. “This chip simplifies the developing of safety-relevant units” accentuated Heinz Gall “and is most of all interesting for medium-sized companies for those the certifying of an own safety-relevant communication interface will be too costly”.

That’s why we need Profiles

For many industrial bus-systems and networks are only available general guidelines for the definition of profiles or make-specific unit-profiles. In the profiles are

• the internal unit-address, the access mode "read" or "write",
• the type of data,
• the permissable co-domain and
• the relevance defined.

Optional the physical units (SI-units), offset-values, and the time manner can be defined. In unit-profiles additional the application features are specified. So application profiles defining not only the communication of an unit interface, but also the communication of all equipment in one application. Only by profiles an integrative basis will originate, by which the equipment of different manufacturers can communicate with each other.