I can remember attending exhibitions back in the late 1990s where brave souls displayed the first tentative products for networking industrial systems via Ethernet - a standard networking protocol that had been at the very heart of office and commercial information flow for years. I say 'brave' because industry was still confused by the choice of purpose-designed 'fieldbus' networking protocols such as Profibus, DeviceNet, InterBus-S and the like - all of which had been developed specifically to cope with industrial automation demands. What was this upstart Ethernet from the commercial sector going to bring to the party? And was it anywhere near capable of providing that all-important 'determinism' that industrial users, willing to shun the hard-wired alternative, craved?
It took a long time to catch on. Clearly there was work to be done to turn this fast but 'flawed' (as far as industrial automation is concerned) protocol into a viable 'industrial fieldbus' in its own right. In fact, it took a number of years persuading the big players to take it seriously, but their input has had a big impact and the likes of Mitsubishi, Rockwell and Siemens, along with numerous smaller specialist companies, have ensured that the market takes notice. Steve Jones of the CC-Link Partners Association offers this succinct technical definition:
"Industrial Ethernet uses Ethernet as the data link layer protocol in the OSI seven layer model with a fieldbus protocol as the application layer. This is conceptually similar to the various fieldbus options that use RS232/485 as the data link layer, with the fieldbus protocol itself at the application layer."
There are many advantages of moving to industrial Ethernet, not least of which is a vast increase in speed - up from the sub-10kbit/s typically with RS232, to the gigabit and beyond potential of Ethernet. Overall performance is also increased, and costs are significantly reduced because Industrial Ethernet is able use standard access points, routers, switches, hubs and cables, which are considerably cheaper than equivalent serial port devices. Other advantages include the use of peer-to-peer rather than master-slave architectures. But there is more to it that that, says Steve Jones.
"The biggest advantage aside from cost is the significantly greater interoperability between devices offered by industrial Ethernet. In particular, there is the potential for a seamless flow of data from field devices all the way up to higher level business systems, and back, delivering huge gains in flexibility for manufacturers looking to boost their productivity. And for users who take their use of industrial Ethernet to its ultimate potential, there is the possibility of using a single, standard network for information, configuration, control, safety, synchronisation and even real-time distributed motion."
It is perhaps the evolution of Ethernet technology from a 10Mbit/s bus/tree topology to a gigabit, switch-based topology (like that adopted by the CC-Link IE protocol) that has smoothed the path for users wishing to implement Ethernet on industrial time-critical applications. Indeed, the switch-based topology makes an industrial Ethernet network very different from a device-level network.
The infrastructure of Layer 2 and Layer 3 switches is the core of the industrial Ethernet network, providing the determinism and throughput required for dynamic control applications. The switch's ability to eliminate data collisions is the most important mechanism in the provision of 'real-time' capability for Ethernet-based control systems. Switches can be added to split the data load between segments, resulting in higher performance. In addition, managed switches can prioritise network traffic, allowing the preferential handling of real-time elements over supervisory functions.
Of course, an industrial Ethernet switch is a very different animal to that which is used widely in office environments. Industrial switches are usually housed for rail mounting in cabinets and are likely to be rugged enough to permit location close to the controlled process or even direct attachment to machines.
Also available are highly protected versions of the standard Ethernet RJ45 connector, which will be mechanically superior in construction terms, as well as being impervious to dust, moisture and aggressive wash-down fluids.
The industrial Ethernet switch also facilitates easier, less costly implementation of redundancy, compared with the conventional fieldbus approach. This is possible thanks to 'dual homing' technology, which can be built into even the smallest of switch products to provide affordable redundancy for nodes out at the edges of a network.
Unlike typical device or control level networks, which generally have a passive infrastructure that limits the number of devices that can be connected and the way they can be connected, the industrial Ethernet infrastructure can accommodate a virtually unlimited number of point-to-point nodes, providing users with enormous flexibility in terms of current network design and planning for future expansion.
Recent hardware developments, moreover, have removed the communications distance limitations that have been a recognised issue with the move to gigabit Ethernet. There are new switches available (such as the CSG14 converter from GarrettCom) that enable industrial installations with multi-mode fibre to achieve 2,000m gigabit connectivity. Previously, only 10/100Mbit Ethernet could be transmitted over these distances using multi-mode fibre and you had to go to single-mode fibre cable for the gigabit rate. Users looking to upgrade have hitherto been forced to rework their network installations around shorter transmission distances and/or single-mode topologies, at great expense. The new switches have overcome these problems and made the upgrade path far simpler and more cost-effective.
Growth prospects
According to the well-respected automation industry observer, ARC Advisory Group, the market for hardened industrial Ethernet switches and other types of Industrial Ethernet network infrastructure will grow steadily, reaching nearly $1bn in value by 2011 (from around $260m in 2006). While Ethernet has captured a growing share of the global automation networking market, recent ARC research shows that many other types of industrial networks have also been expanding during the past two to three years.
Some and perhaps many of the applications now served by the various industrial device networks and motion control networks will eventually migrate to industrial Ethernet. As machine automation system designs evolve to use more Ethernet-based devices, the market for Industrial Ethernet switching will inevitably grow as well. Presently, we are only seeing the tip of the iceberg as Ethernet reaches only a fraction of the devices that are currently connected to industrial networks.
According to ARC senior analyst, Harry Forbes, Ethernet continues to grow into a greater number of application areas within manufacturing. While Ethernet will never entirely replace device networks, he says, it will continue to pick up more applications over time. In particular, he identifies a trend for devices to embed some form of Ethernet switching internally, especially in motion control. This might blur the distinction between an industrial device and an Ethernet switch at some point in the future, but ARC remains convinced that double-digit growth for industrial Ethernet switching will be sustained into the foreseeable future.