Last month’s ARC Advisory Group column dealt with server-level virtualisation in CPAS, ARC’s collaborative process automation system model. Server virtualisation has become part of mainstream IT, and most server virtualisation technologies and benefits map directly into CPAS at the server level. Here, we address the impact virtualisation has on process controllers, I/O systems, and process field devices; the parts of an automation system implemented as embedded systems.
An embedded system is traditionally defined as a dedicated function device containing electronic hardware, a microprocessor and specialised software. The relatively complex embedded systems found in process controllers employ microcontrollers or full-fledged microprocessors. They are networked and may download their operating system and application software via network services.
With the development of multi-core microprocessors, semiconductor suppliers can now support virtualisation technology within a single microprocessor. In effect, the software stack of a server can now be replicated within an embedded system. Process automation, with its very long product life cycle, stands to benefit from the broad adoption of embedded virtualisation in other industries, such as automotive, aerospace and medical equipment. Process automation suppliers are now planning products that will use this technology.
ARC believes that embedded virtualisation will have a major impact on our evolving CPAS vision.
Embedded virtualisation and NextGen controllers
Process controllers are perhaps the most complex and multi-functional components of any process automation system. To meet the extremely high requirements for reliability, they incorporate complex and proprietary means for hardware fault tolerance. Process controller software has always run on various real-time operating systems (RTOS). The next generation of process controllers will be able to exploit multi-core processors and embedded virtualisation.
ARC believes these factors will weigh in the development of future CPAS controllers with embedded virtualisation:
Higher performance – the additional compute capacity of multi-core processors with virtualisation could be employed simply to improve the capacity and/or performance metrics of a process controller.
Greater application integration – controllers running both an RTOS and a rich OS will be able to host CPAS applications that presently can only be hosted in servers. Advanced process control and optimisation are certainly applications that may fit into this configuration. Data historians and local analytics may fit as well.
System management – process automation systems have traditionally provided their own (proprietary) system management capabilities. Given extra processing capacity and a rich OS, these could be incorporated into standards-based management protocols, which could aid in giving automation system status wider visibility in the enterprise.
Advanced networks – several process automation suppliers have developed high-availability Ethernet networks at the controller (peer-to-peer) level. In NextGen controllers, these networks may extend to the I/O systems and perhaps even to field devices. Networks can also be virtualised, and silicon suppliers have developed technologies for doing this at the embedded system level. Such virtualised network interfaces could be provisioned to support both real-time and rich OS network traffic.
New controller modularity options – process controllers represent a combination of high complexity and low unit volume. System designers are challenged to optimise not only performance, but product lifecycle length, TCO, system BOM costs, commonality of system hardware, and commonality of system software. ARC believes that in the long term, commonality and component life will weigh more in this equation. This would favour new systems incorporating higher performance processors and more common software.
I/O system and field device applications
Process automation I/O systems can share some of the same benefits from virtualisation, but not to the same degree as controllers. The industry trend in I/O systems has been toward ‘smart’ I/O modules that are configurable (via software or a hardware adapter) to accept multiple types of signals. This capability has proven very valuable in compressing automation project schedules by decoupling detail engineering from other project activities. Expanding smart I/O capabilities is essentially a ‘smart analogue’ technology development that will not be enhanced by virtualisation.
Process field devices (transmitters, valves, drives, analysers, etc.) have remained largely immune from virtualisation benefits. This is mostly because of the age and limited capabilities of the network technologies serving process field devices (HART, Foundation fieldbus, Profibus PA). Adoption of Ethernet networking by process field devices will open up device communication to all manner of improvements and deeper integration, but adoption will be gradual. A field network consisting of a switched Ethernet infrastructure could remove many of the barriers and difficulties end users experience with managing thousands (or tens of thousands) of process field devices.
Given the very long device product development and operating lifecycle, Ethernet field networks will emerge very gradually in the process industries.
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