Figure 1: Parallelization of development through virtual commissioning. © MathWorks

The following points have proven to be useful for getting started with virtual commissioning and model-based development in general:
- Start with reduced complexity of the simulation model and successive expansion throughout the project.
- Modeling or virtual commissioning of a sub-component of the machine or system in the first project (achieve quick wins).
- Gradual introduction of model-based development and replacement of established development processes (change management).

The modeling

The effort required for modeling depends on several components. The detailed modeling of the individual components, for example drives, sensors, etc., of a system provides the most accurate results - but at the expense of modeling and simulation time. A 3D behavior model of the entire system can be helpful for the verification of logical software parts, but is not suitable for the evaluation of physical results, for example the accuracy of a position control or the correct design of the drives.

Simulation environments such as Simulink therefore offer different modules for modeling, which map the individual aspects accordingly. For example, logical state models and step chains are modeled in Stateflow, while Simscape offers the option of importing 3D CAD data as a physical model.

The simulation model of the machine or system created in this way (Fig. 2) is then used in several steps throughout the entire development and commissioning period in order to continuously verify the interaction between the mechanical, electrical and software systems:

Desktop simulation: The behavior model of the machine is simulated together with the algorithms that will later run on a PLC or an industrial PC, for example sequence controls, control technology or AI algorithms. This involves running through different scenarios that would not be possible on the physical machine or would only be possible with great effort.

Figure 2: Simulation model of a handling robot. © MathWorks

Code generation: Source code in various languages is generated from the simulation model at the touch of a button, which is then transferred to the industrial control system and executed there in real time. Optionally, the documentation for the software can also be generated. Model-based development with Simulink supports the common industrial control platforms.

Hardware-in-the-loop: The portion of the simulation model that represents the physical and logical behavior of the machine or system is also used to automatically generate real-time-capable code that runs on real-time hardware connected to the PLC via common industrial protocols (Figure 2). This simulates the behavior of the system to the industrial controller so that different tests can be carried out under real-time conditions.

This workflow has not only been established in the automotive industry for years, but is also used successfully in mechanical engineering by leading companies such as Krones, Metso and Tetra Pak.

Model use beyond virtual commissioning

The models developed for virtual commissioning also offer decisive added value beyond the development and commissioning phase. They are increasingly being used as so-called digital twins - i.e. virtual representations of the running system - over the entire service life of the machine. Typical applications here include predictive maintenance or the prediction of quality fluctuations based on a comparison of measured and simulated data. The digital twin is usually embedded in the IT infrastructure of the production plant. Tools such as Simulink offer corresponding options for the use of models on edge or cloud systems.

In times of increasingly complex systems, virtual commissioning helps mechanical engineering to virtualize commissioning to a large extent, thereby saving time and costs. With the help of model-based development, the simulation models created in this way are used throughout the entire development phase - and increasingly beyond in the form of digital twins. With the gradual introduction of virtual commissioning and the appropriate software tools, this step usually pays off in the very first project.

Philipp Wallner, Industry Manager at Mathworks / ag