Execution of the security application in two separate software channels using transformed code. © Codesys

While the first products using coded processing in the early 2000s were still too slow for industrial applications, today’s versions—with significantly more powerful processors and optimized software algorithms—are ideally suited for such applications. Although such a system is slower than one without transformation, the difference is only by a factor of 5 to 15. At the same time, the elimination of synchronization points as well as CPU and memory tests significantly reduces the load on the processor, in contrast to discrete safety controllers. And because the method is hardware-independent, it is possible to switch to a more powerful computer architecture at any time if necessary—something that is not possible with physical safety controllers.

Using vPLCs and vSafePLC

Using both functional and safety controllers virtualized in a container provides a twofold benefit. A vPLC such as Codesys Virtual Control SL already offers new flexibility—simply through the freedom it provides regarding the underlying hardware and the ability to instantiate it independently on that hardware. Codesys Virtual Safe Control SL additionally covers the safety function. The patented SIListra Safety Transformer has been integrated for code processing. vSafePLCs can also be deployed as often as needed and with fine granularity—on the same platforms as the vPLCs. Here, too, I/O access occurs in real time via Ethernet protocols. For safety-critical applications, secure protocols such as Profisafe (F-Host / F-Client) and FSoE (Fail Safe over EtherCAT) are available and can be configured directly within the Codesys Development System.

Screenshot of the CodeSys development system with a SIL3 application (right) on a virtual safety controller (on the left in the tree). © Codesys

Virtual controllers can be deployed on the target system and managed ("orchestrated") using IT tools or simply with the Deploy Control SL add-on included in the Codesys Development System. The virtual controllers are included in the prepared image. For safety-critical applications, an additional image with integrated vSafePLC is available. The system automatically handles the division into the two independent channels as well as the execution and monitoring of the safety application in the background. Functional and safety applications are programmed directly in the Codesys Development System, typically within a single project. This allows data to be easily exchanged between the two PLCs. The purely functional part is expanded by an additional, certified add-on featuring a safety-compliant IEC 61131-3 editor for the safety application. A process certified by TÜV Süd monitors the download of the generated code to the virtual safety controller. The administration of virtual functional and safety controllers is thus largely standardized.

With regard to safety certification under the Machinery Directive, the procedure for vSafePLCs is identical to that for physical safety PLCs, with the exception that certified safety hardware is no longer required. TÜV Süd certified the base software of Codesys Virtual Safe Control SL for SIL3 applications on x86-based architectures as early as January 2025—specifically independent of the executing hardware. An extension to ARM-based systems is even planned for the middle of this year. As a result, Codesys Virtual Safe Control SL offers manufacturers—and especially operators—of machines and systems additional freedom—now even for safety-critical applications. The virtual controllers Codesys Virtual Control and Codesys Virtual Safe Control are already being used successfully in automotive production lines.

vPLCs in the Field of Motion, CNC, and Robotics

Even time-critical applications involving coordinated motion sequences can be implemented using virtual controllers. Motion applications programmed in tools such as CodeSys are executed using servo drives that are controlled via a fieldbus, typically EtherCAT. If vPLCs are used as PLCs, motion controllers can also be virtualized and executed within a single software environment. Even long distances between the target hardware and the drives—for example, in robots or gantry systems—can be bridged via Ethernet. vPLCs located on very distant servers can be connected via fiber-optic cables and appropriate converters. An application-specific integrated circuit (ASIC) from Missing Link Electronics, which bundles multiple protocols and transmits them without loss, is nearing series production. A patented method tunnels the data in such a way that all properties and information of the original system are preserved. This means that functionally safe protocols such as FSoE or ProfiSafe can also be used. Importantly for users of motion and PLC systems such as Codesys, unlike other fiber-optic systems, this type of data tunneling does not change the operation or configuration of the system. The circuit behaves like a standard Ethernet card within the system.

Screenshot of the deployment tool for setting up virtual, functional, and secure controllers in the Codesys Development System. © Codesys

Virtual controllers offer numerous advantages and can be used in a wide variety of applications, including safety projects and complex motion applications. All requirements are addressed in software, independent of hardware. The way they are used does not differ from physical controllers, because tools like Codesys provide a unified configuration platform. Ultimately, it is up to companies to test these new possibilities for themselves and realize their full potential.