Three Steps to Creating Digital Twins with the FVA-Workbench

The digital description and representation of the gearbox is addressed by modeling and calculation of the gearbox in the FVA-Workbench. This was implemented as part of William Gunawan’s dissertation on “Creation of a Digital Twin through real time integration of the FVA-Workbench” at the TU Darmstadt pmd. The thesis was supervised by Prof. Dr.-Ing. Eckhard Kirchner and Michel Fett. The project can be divided into three steps: modeling the gearbox, establishing live calculations, and visualization in a dashboard. The following is an overview of the project and the knowledge that was gained.

Step 1: Modeling First, the gearbox was modeled in the FVA-Workbench. The two gear pairs of the two-stage gearbox were used for this purpose. The geometry of the individual gears was described along with the material parameters. This includes, for example, the number of teeth (z), module (m), helix angle (b), tip diameter (da), and reference diameter (d) of the individual gear stages. The three shafts of the gear stages were also described by defining the material parameters, center distances, and geometries of the individual shaft shoulders, among other things. The bearings and the gear oil could be selected as standard components from the FVA-Workbench library. The gearbox casing was not modeled, as CAD data for the casing was not available in the project. Step 2: Live Calculations Typical use of the FVA-Workbench involves one-time simulation of the behavior and characteristics of the modeled gearbox and creating a report from the results. However, digital twin functionality requires continuous, cyclically recurring live calculations. This can be achieved using the FVA-Workbench’s scripting feature, which can automate the execution of calculations. To do so, a script was created which uploads the latest measurement data from the sensors mounted in the gearbox to the TU Darmstadt server in 10 second increments. This measurement data includes the current torque and speed values, which are then used as input variables for calculations in the FVA-Workbench. Thus, the current behavior and status of the gearbox are calculated every 10 seconds.

Step 3: Visualization

Creating a results report every 10 seconds is not useful for the purpose of a digital twin. Instead, the FVA-Workbench exports the calculation results as Excel files. A live dashboard was created directly in Excel using VBA (Visual Basic for Applications), which is updated regularly with the latest calculation results and shows the current status of the gearbox. For example, the load distribution on the tooth flanks and the load ratio C/P of the bearings are visualized. The plots in the dashboard are updated after each new calculation in the FVA-Workbench.