## 5 Testing and Verification of the Virtual Commissioning Model  
The developed virtual model as the digital twin of the assembly system was prepared for testing and verification within the virtual commissioning framework. Following the creation of 3D models with defined logical behaviour, the layout of the automated assembly system was established. Figure 21: Generated material flow of individual assembled parts. The diagram illustrates the flow of silver, black, and red cylinders through the feeding and extraction operations. The layout configuration is a crucial step that takes place prior to virtual commissioning, ensuring proper alignment of the simulation model with the PLC control system before establishing their connection. This phase ensures that the spatial arrangement of components is optimized for seamless integration between the virtual environment and the real-world automation system. The methodological approach to virtual commissioning was thoroughly developed for a single device within the entire assembly system to ensure clarity and a simplified process demonstration. The layout configuration is based on a 3D design of the entire system, created in a CAD environment. Virtual commissioning is carried out by connecting the simulation model, incorporating all the attributes mentioned in previous sections, with the PLC control system (either virtual or physical) through standardized interfaces such as OPC DA, emulators, or bus systems. Once the connection is established, it can be tested via the \"Sequence Editor\". This editor allows for the testing of individual operations, either in time-based or event-based simulation modes. Additionally, it enables the generation of movement and paths for industrial robots, tools, and products through the \"Path Editor\". The \"Sequence Editor\" essentially functions as a Gantt chart for the operations created in earlier steps. Control is facilitated through buttons like Play, Pause, Reverse, and Forward, with the ability to adjust simulation accuracy and speed based on time requirements. By clicking the Play button in the sequence editor, the simulation is initiated. However, the step size between two simulation times must first be specified. This requirement significantly impacts the accuracy of the simulation. Once the simulation is started and a PLC connection method is selected, the system automatically proceeds. In this case, Siemens PLCSIM is used for the PLC connection. The tested control program communicates with the virtual model via PLCSIM. A valuable tool for testing the control program is the \"Simulation Panel\". When the simulation model is in \"online\" mode, the virtual commissioning of the assembly system can be applied and tested. In this way, a simulation model of the entire assembly system can be created. Individual virtual models, whether with defined kinematics and behaviour models that will move or virtual static models (such as tables, barriers, etc. ), must be imported into the project separately. In Process Simulate, imported objects can be repositioned using the \"Manipulator\" function, allowing precise arrangement of system components. The assembly system model was fully developed in Tecnomatix Process Simulate, where the entire process was simulated and verified using time-based simulation. The model is now prepared for event-based simulation testing, ensuring its readiness for further validation and optimization, as shown in Figure 22.  
As shown in Figure 23, the virtual commissioning of the assembly system can be characterized as a simulation model that integrates both the virtual system model and the control system. The virtual system model includes digital representations of objects, system layout, and material flow, while the control system consists of a PLC, a control program, and an HMI panel. This integration enables a comprehensive validation and testing environment for the automated system before physical deployment.