Conception of a digital twin for Kroenert GmbH & Co. KG
Industries: Plant Engineering and Machine Tool Industry
Kroenert GmbH & Co. KG is a manufacturer of coating, printing, and laminating systems with an international ambit. Based in Hamburg, the company builds on its 110-year history to supply turnkey system solutions for coating technology used with materials in continuous form such as paper, foil, and film. The product range includes complete plants, in addition to an extensive range of unwinding and rewinding units, more than 60 modular coating systems, and driers, moisteners, and laminating machines.
Kroenert engaged Heitec to generate a digital twin of the unwinders and rewinders to improve development, production, and commissioning. At the same time, it had to be possible to set the simulation parameters in real time in order to accommodate the high level of variety in the machine fleet.
All the participants first gathered together to drive forward development of the simulation model. It quickly became clear that the normal approach using a top-down model and a fixed set of specifications would not work. If minor details have to be assessed or aspects of system design need to be revised, for example, the engineering process must run through repeated, costly iterations, which can lead to errors that may be detected only when the system is put into operation. That’s why the development team opted for an agile development process, and broke the complex project down into many small steps, each with its own deadline and a defined function. The transparency achieved in this way was used to review the entire project and adapt it in response to new information. The foundation of the project therefore took the form of a strongly modular, object-oriented collaborative development based on project and driver generators. The Covid-19 crisis which began in March 2020 demanded additional creativity from the team of developers. For a time, module development and validation took place in parallel between three locations across Germany. The hardware-in-the-loop test structure was duplicated for this purpose, and software status was regularly synchronized using update mechanisms. Because the project involved systems associated with the flow of paper, foil, or film, it was essential to represent and develop the processes as realistically as possible in a simulative environment. After all, the controller functions can be validated only if the entire machine fleet is also reflected simultaneously in a real-time simulation. In this connection, however, it was essential to ensure the Kroenert systems maintained a one-millisecond process-based controller clock cycle: Each simulation step had to take place within a maximum of one millisecond. Based on the REFA workflow principle, this level of performance is achieved only if all the other modules – up to twelve in total in this case – are simulated together with a one-millisecond clock cycle. At the same time, it had to be possible to set the parameters for the simulation in real time in order to accommodate the high level of variety in the machine fleet. That created new challenges for the specialists from HEITEC, since they had to develop a machine model that could be parameterized in real time for both the drives and for other machine components and for the process simulation. This then made it possible to adapt parameters both manually and automatically while the simulation was running, without having to stop and start it again. This controller-based real-time simulation is the latest HeiVM development. It uses validated mechatronic toolboxes and communications modules which were tested during real commissioning processes, and implements them in dedicated, real-time-capable controllers and controller emulations. This has two benefits: A PLC interface for the high-level language-based toolboxes, which the PLC programmers will recognize and can use as a familiar working and development environment; and HeiVM adopts the controller architecture, which makes it easier to exchange signals based on the REFA principle. That also means the virtual machine model speaks the same language as the controller project.
The computing power of the latest controllers has now advanced to the point that their multicore and threading capability enables them not only to describe the drive, behavior and controller models deterministically, but also to establish specific simulation tasks by priority and cycle time. In turn, that resulted in the ability to work through the entire behavior model externally and thus take the load off the correct real-time-capable simulation tool for the task during the virtual commissioning process. Moreover, the controller still had enough performance to integrate the complex material flow into the simulation. Overall the result was a critical gain in performance, which enabled us to create a simulation that satisfied Kroenert’s technical performance requirements.
Working together with Kroenert, we were able to validate the feasibility and the use of digital twins for the kind of in-depth process tasks that are standard at Kroenert. By duplicating the hardware-in-the-loop test structure and synchronizing software status using an update mechanism, it was possible to simultaneously review the newly created modules at Kroenert for functionality and performance while the HEITEC team in Erlangen and their home offices gradually expanded the modules and refined others. In this way, up to three developers were able to work successfully on different functions at different locations in parallel. This produced a substantial efficiency boost for the development process. This new strategy for success, matured in close collaboration, will now be expanded to cover the entire modularized machine fleet. The modules will be further honed and definitively validated. The goal is to fully reflect the new simulation methodology on the entire machine fleet in real controller time, using a single simulation unit with no need for additional hardware.