Commercial technologies in the consumer and information technology (IT) space typically advance faster than for operational technology (OT) products. However, Emerson has made great strides applying IT-type virtualization into OT platforms. My article in Control Engineering, Industrial Virtualization Heads to the Plant Floor, discusses how this works and the many benefits.
Use of virtual machines (VMs) is mainstream for many OT products, practices, and applications, mostly hosted on PCs and servers. Virtualization helps engineers efficiently develop, test, deploy, and maintain systems. Now, Emerson has developed products and technologies to merge virtualization with more traditional programmable logic controller (PLC) and programmable automation controller (PAC) platform capabilities.
Virtualization ConceptsVirtualization is basically the ability to independently run more than one VM operating system (OS) on a single hardware platform.
This is made possible by a hypervisor, which is a combination of hardware, firmware, and software allocating the hardware resources. Desktop PCs often use Type 2 virtualization, where the hypervisor is hosted on a traditional OS. For better performance, Type 1 virtualization allows the hypervisor to run natively on the “bare metal” hardware. Only recently has virtualization become practical for the plant floor.
Industrial Controllers and VirtualizationConventional PLCs and PACs use dedicated a hardware and specific real-time OS (RTOS) to provide high-speed deterministic control. Preserving real-time control in conjunction has been a challenge, which Emerson has overcome by developing the industry’s leading edge controller.
By using multicore hardware and Type 1 virtualization, an advanced edge controller combines a RTOS “inner loop” for robust control with a second general-purpose Linux guest OS “outer loop” (operating similar to a PC) available for edge processing and other tasks.
A helpful analogy is found in the operation of a car. The driver is the mission-critical inner control loop, while a dashboard navigation system is a valuable, but not essential, outer loop providing helpful information.
Control Remains in the Inner LoopThe RTOS inner loop performs direct control with millisecond performance, much like a PLC or PAC. It can monitor sensors like flow transmitters, can be programmed in many IEC 61131 languages, execute PID loop control, and command devices like flow control valves.
Extended Capabilities Live in the Outer LoopThe general-purpose OS Linux outer loop can perform supplementary tasks, really anything a dedicated PC could do. Some applications:
Other Controller Virtualization ConsiderationsThe two OSs operating in one edge-located controller are independent but can interact securely via OPC UA. The edge controller hardware is packaged in an industrialized form factor, rigorously isolating the two VMs and their respective Ethernet ports. The combination can easily and securely communicate with supervisory and cloud systems, while edge processing unloads all upstream systems.
Future-Proofing Through Controller VirtualizationVirtualization of industrial systems in the form of a true edge controller consolidates devices at the edge, safely delivering performance gains with cost savings.
End users often prefer the controller virtualization approach because it gives them the same controller-type functionality they need and use today, while adding an optional layer of computing. This future-proofs their designs because they can grow as needed without expensive hardware replacement.
Some end users see controller virtualization as analogous to their smartphones, which are first and foremost a phone, but can offer many more useful functions in the future as apps are added.