## 4 Digital Twin and Control System Design
### Geometry and Kinematics Model  
A 3D geometric model not only meets technical requirements but also enhances visualization, improving user acceptance of virtual commissioning. When a PLM system is integrated within a digital enterprise, and digital models are utilized comprehensively (e.g., Siemens Teamcenter PLM 13), no conversion between CAD models across different software platforms is necessary. Figure 4: The first phase of digital twin design: integration of the physical 3D model (geometry and kinematics) with the logical behaviour model to generate a virtual model. Figure 5: Diagram illustrates the systematic methodology for digital twin development, control system integration, and virtual commissioning in industrial automation. In the absence of a unified PLM platform, various software tools must be used for CAD data conversion. To facilitate seamless data exchange between different software environments, open standards such as STEP and VRML are commonly employed. Consequently, most software vendors provide dedicated import/export interfaces, ensuring interoperability across platforms (Table 2). This applies to so-called \"raw\" models (i.e., unprocessed data) that lack kinematics or sensor integration, both of which are essential for virtual commissioning. Kinematic conversion is currently either not supported or only partially enabled through the AutomationML format. AutomationML is an open standard designed primarily for data exchange in the engineering process of manufacturing systems across different software platforms. It facilitates interoperability by standardizing model representation, enabling seamless integration within heterogeneous digital environments [75; 76]. In this case, the STEP format was the only available model format, requiring conversion before integration into the simulation environment. To achieve this, the CAD software NX 2406 (Siemens AG, Munchen, Germany) was used to transform the model into the JT format, which is the required import format for Tecnomatix Process Simulate. This conversion ensured compatibility and enabled seamless integration of the 3D model into the virtual commissioning workflow. Since Process Simulate operates with a model database and supports model imports exclusively in the JT format, the models must be stored in a monolithic structure within a directory formatted as COJT, as shown in Figure 6. This requirement ensures proper integration and compatibility within the simulation environment, allowing seamless manipulation and interaction of the digital twin components. As the test model for virtual commissioning, the \"Distribution\" station of the MPS(r) 203 I4.0 system by Festo Didactic was selected. This station serves as the digital twin, enabling direct comparison with the physical MPS(r) 203 I4.0 system. The station is an integral part of \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Software** & **WinMOD** & **Delmia Automation** & **Process Simulate** \\ \hline To Import & VRML & VRML, STEP, CATIA/DELMIA V5 format & VRML, Siemens PLM format (jt) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparison of software tools for virtual commissioning and their supported CAD import formats. Figure 6: Three-dimensional digital twin model of the MPS® 203 I4.0 assembly system, prepared for integration into the simulation environment. the assembly system, designed in accordance with the Industry 4.0 reference architecture, ensuring compliance with modern cyber-physical production principles. The \"Distribution\" station is responsible for feeding cylinders of various materials and colours onto the conveyor belt. This task is performed by an automated feeding device controlled by a pneumatic cylinder DSNU-8-100-PPV-A (19182), Festo AG & Co. KG, Esslingen, Germany (Figure 7). The pneumatic actuator ensures precise and repeatable handling of the components, supporting the automated material flow within the assembly system. As previously mentioned, Process Simulate operates with models stored in a database following a predefined format.