Wireless Process Control Times Have Changed for Wireless Process Control
Fast and easy data integration into control systems: wireless communications in Brownfield applications—When it comes to using wireless technology in the process industry, system operating companies have objected for a few years now that wireless communication is too insecure in terms of reliability and security. In addition, they believe that data is transmitted too slowly. But the times have changed!
A glance at the applications in which data is transmitted wirelessly quickly reveals how diverse the fields in which these different technologies are applied really are. Admittedly they have not made inroads in time-critical control systems.
Yet, all chemical parks like to use wireless protocols for the purposes of surveillance, diagnostics, asset management, or connections to distant stations. The differences lie only in the scope of the wireless data exchange.
Most applications, however, are Brownfield applications, meaning existing systems that are optimized, expanded, or overhauled in another way. If technologies such as Wireless Hart are used in these systems to glean additional information from the process in the fastest and most cost-effective way, thereby enabling optimization, then the advantages of wireless transmission can only be realized if the data can be quickly and easily integrated into the control system. Problems often crop up at this point.
Mapping Hart Communication in the Profibus Protocol
All of the Wireless Hart gateways currently offered support Modbus and often TCP as transmission protocols. The integration of process data turns out to be simple because newer control systems have the corresponding interfaces.
However, several older systems are still working with control system versions that are less communicative. If connections are possible at all, then they can be done via Profibus. In this context, Phoenix Contact has developed a simple solution for mapping the most important parts of Hart communication in the Profibus protocol.
How Wireless Hart Communicates with Network Components
The solution is comprised of a wireless gateway, a controller and a bus connection, whereby the Profibus connection can be designed in copper or fiber optic technology (Fig. 1). The controller software checks the Wireless Hart network dynamically and provides regular information in the form of a status word about the network name (network ID), the number of currently connected wireless users, as well as the status of the various network components (Ethernet, Profibus, Wireless Hart) or gateway components.
To identify the individual field devices, the long tag — meaning the name of every participant — is transmitted along with the respective NE-107 status, with additional battery information for the adapters or field devices if needed. This enables even older controllers to use part of the asset management data.