A new solution is setting new standards Profinet - the medium of the future up to field levelEthernet gave its debut in industrial communication about 20 years ago as Sinec H1 from Siemens. Now this bus system, in the Profibus version, is the trend for networking all levels of industry.

The increasing importance of the vertical integration and the trend towards distributed automation structures equally demand new solutions for industrial communication. The most promising solution is Profinet, the open Industrial Ethernet standard of the Profibus User Organization. Profinet supports the implementation of a complete and homogeneous automation solution based on Industrial Ethernet. Profinet relies on established IT standards and supports TCP/IP without restrictions. This guarantees homogeneous, company-wide communication throughout all divisions.

The architecture - from the master-slave method ...

In the Profinet architecture a distinction is made between Profinet IO and Profinet CbA (Component based Automation). Distributed field devices can be integrated directly in Ethernet with Profinet IO. The master-slave method familiar from Profibus becomes the provider-consumer model. Although, from a communication point of view, all devices on Ethernet are equal, the field devices are permanently assigned to a controller by the configuration. The normal IO view of Profibus DP is retained, i.e. the useful data of the field devices are transferred cyclically to the process image of the controller. The device model described by Profinet which is oriented to the basic features of Profibus DP, consists of slots and channels. The properties of the field devices are described by a General Station Description (GSD). Profinet IO is engineered exactly the same as system integrators of Profibus DP are used to.

Profinet IO distinguishes between the three types of devices IO-Controller, IO-Device and IO-Supervisor. The IO Controller represents the controller in which the automation program runs. IO Devices are the field devices assigned decentrally to the IO controller. And the IO Supervisor is the programming unit/PC with commissioning and diagnostic functions.

In the data transfer between IO Controller and IO Devices cyclic useful data and energy controlled alarms can be transferred by the realtime channel. Diagnostic data are parameterized, configured and read via the standard channel based on UDP/IP.

... to distributed automation

The nucleus of Profinet CbA is a component model. It is used in distributed automation systems and is ideal for intelligent field and automation devices with programmable functionality. The component model designates autonomously active sub-units of machines and plants as intelligent modules. A distributed automation system designed on the basis of intelligent modules is optimally suited to modular plants and machines. In addition, the plant and machine parts can easily be reused which considerably reduces engineering costs.

Communication in realtime

Different performance stages are available for communication in Profinet. For time-uncritical transfer of parameters, configuration data and switching information via Profinet, the standard channel is used based on TCP/UDP. This creates the conditions for linking the automation level to other networks (MES, ERP). Time-critical process data within the production plant are transferred by the realtime channel (RT) which is implemented as software on the basis of existing controllers. The Isochronous Realtime Communication (IRT) is recommended for clock-synchronous applications with its extremely fast response times (clock rates below 1 ms and jitter accuracies of 1 µs).

Investment security due to fieldbus integration

An important contribution to the protection of investments for equipment manufacturers, plant/machine builders and end users alike is the smooth transition from existing field bus solutions like Profibus DP to the Ethernet-based Profinet.

Field bus devices can be integrated by so-called proxies. The proxy is the representative of the subordinate field devices on the Ethernet. With the proxy principle Profinet offers a totally transparent transition from the existing to the newly installed plant parts.

However, it is also possible to integrate whole field bus applications. A field bus segment represents a self-contained component - the representative of this component is the Profinet device which operates a subordinate field bus such as Profibus DP. Thus the whole functionality of a subordinate field bus is saved in the proxy in the form of a components which is then available on Ethernet.

IT integration

Profinet offers all the functions from configuration and diagnostics of Profinet devices in Ethernet networks. In the web integration Profinet uses the Ethernet basic technologies and enables access to a Profinet component by means of standard technologies from the Internet sector.

Perspective for the future

The advantages of Profinet are already obvious: low installation, engineering and commissioning costs for the plant or machine manufacturer, possibilities for simple plant expansion and high plant availability for the owner (due to much shorter retooling times). The continuous further development of Profinet offers users a long term perspective for the implementation of their automation tasks. And last but not least, the establishing of certification by the Profibus User Organization guarantees a high quality standard of Profinet products.


Totally integrated thanks to Ethernet

The Elektrolux factory in Porcia (Italy) is the most important production site for washing machines of the Elektrolux Group and, thanks to Ethernet is a fully integrated factory with information exchange on all levels. Vincenzo Peresson, the man responsible for IT systems at Elektrolux in Porcia, about the advantages of this solution.

Ethernet provides us with the possibility first of all of always monitoring the production process in realtime and always manufacturing products just in time and in the right quantities. We can also scan the exact production progress every 15 minutes and react quickly in the event of a fault for example. This transparency also allows collection of data for quality control of course - from any workstation in the plant.

The most important criterion for using Ethernet in industrial environments is reliability. Therefore an industrially compatible Ethernet Switch must have a memory medium on which the configuration data are saved - then it can be changed in a few minutes without the need for a programming unit. Above all in the vicinity of the processing machines you need a connection which is robust but also easy to wire such as the Siemens FastConnect system.

We believe that Ethernet has a good chance of advancing directly to the machine. Only recently we assembled a test plant in which Ethernet is used not only for connecting the controller to the integrated factory network but also in an autonomous subnet of the painting system in which Profinet I/O peripheral devices are installed.