Where now for fieldbus?

As Ethernet gets a grip in automation, what is the future for fieldbus? With the possibility of the now standardised protocols losing out, the race is on to be the protocol of choice on Ethernet, with all the old favourites entering the fray

Another revolution in automation is happening, with greater opportunities for those prepared to act quickly. Open solutions are now a fact of life with Ethernet promising to be backbone of sensor to boardroom integration. The pace of change on the plant floor is set to increase, with many automation manufacturers having positioned themselves to provide this shop floor to top floor transparency. Ethernet appears the logical choice for the intelligent building backbone, with applications already installed utilising industrial components. With the introduction of IEC 61508 (Functional safety of electrical/electronic/programmable electronic safety-related systems) safety-related technologies are no longer held back, allowing development of machine safety fieldbus which will fundamentally change machine safety systems.

With the possibility of the now standardised protocols losing out, there is a race to be the protocol of choice on Ethernet, with all the old favourites entering the fray, including Ethernet/IP (DeviceNet/ControlNet), Interbus (hybrid), Modbus/TCP and ProfiNet (Profibus). Invested interests ensure all your needs will be catered for should you wish to take the plunge and try Ethernet. There are others promoting open systems, and the Industrial Automation Open Networking Alliance (IAONA) is a relatively new trade group that has combined formerly separate European and American operations to encourage the growth of open networking in industrial automation. IAONA has recently announced an agreement involving the Interface for Distributed Automation consortium (IDA, promoting distributed intelligence for greater modularity, horizontal and vertical integration), and the Open DeviceNet Vendor Association (ODVA), leading to a common strategy for future development of Ethernet products for Industrial automation. These developments have industry-wide support and offer a real prospect of interoperability between different flavours of Ethernet.

All this cooperation is working to remove implementation barriers to industrial Ethernet networks. IAONA will be the umbrella organisation and will coordinate technical working groups and publish solutions as IAONA specifications prior to submission as standards. Despite this, the Nirvana of a single fieldbus standard still remains unlikely. Ethernet does not answer all our prayers, in the same way individual fieldbus technologies do not meet all our needs. Ethernet is not suitable for the simple sensor, leaving plenty of scope for sensor/device networks.

The next race, your choice for safety fieldbus has a small number of front runners now, with many more due on the market before the end of 2001. Users will be able to choose systems that are suited to small or large scale implementations, with the benefit of separation, combination or interfacing with existing conventional fieldbus devices.

Safety-related fieldbus offers significant advantages over traditional hardwired safety systems, that should now be familiar to fieldbus exponents. Wiring complexity is reduced, along with the associated design, commissioning and installation costs. Distributed intelligence down at the device level allows rapid fault diagnosis and rectification which saves significant additional engineering expense. Further savings are likely as the range of safety devices increases from I/O, emergency stops and light curtains to include safety-drives and robot interfaces.

Will Ethernet be used for safety-related applications? The answer is yes, and it is available now for critical process control. Many of the existing protocols are being developed with an additional safety layer, whilst the same protocols are also being developed for Ethernet. A combination of the two is inevitable. Ethernet will increase the impact of PC control, but will not necessarily be recognisable as an industrial PC or a white box, allowing the use of web browsers for HMI applications for instance and the ability to extract shop floor data easily into e-business applications utilising OPC. As one vendor insists, "the network is the controller".

• ARC Consulting
  Email: a156@industrialnetworking.co.uk