## 4 Implementation and Validation DT in AS Ecosystem  
One of the challenges in using modelling and simulation software, particularly when employing high-level modelling approaches with predefined elements from internal libraries, is the limitation imposed on customisation and flexibility. It is the case with industry applications for building DT models. This becomes evident when a low-level modelling approach is required, which involves building new components or mechatronic systems using CAD data and focusing on assembly and functional interactions between various elements. This is the case for the project from this paper developed in AS (a physics-based modelling and simulation tool with workshops such as pneumatic, hydraulic, electrical, and control), where the analytical and dynamic behaviour of the entire model can provide significant added value for a pneumatic mechatronic system. The process follows a V-diagram, as shown in Figure 5, starting from requirements powerfully linked with the tasks of the pneumatic robot from physical space up to the validation and optimisation of DT through the VC approach. The 3D model is changed into a simulation model as the first step towards obtaining a digital twin. To accomplish this, 3D models (with an.igs extension) must be imported  
Figure 5: V-model of implementation in AS—reinterpreted from [1]. into the AS--3D workshop. After, it is necessary to define the required rigid and collision bodies and create the type of displacement for each joint--Figure 6a. Virtual commissioning can be performed using software-in-the-loop simulation (SIL) or hardware-in-the-loop simulation (HIL). The role of a PLC in the digital twin model is two-fold: it provides real-time data to the digital model and allows for the virtual testing and optimisation of control system logic, notably streamlining the process of virtual commissioning. The PLC simulator from AS is used in the SIL simulation to control the virtual robot. The PLC program is checked and runs in a real PLC linked to the virtual robot developed in AS, which runs on the PC during the HIL simulation. Because the model of PLC is not included in the PLC library from AS, it is necessary to work with a generic PLC that closely matches the specifications of a real PLC from an I/O point of view. The communication configuration between the real PLC and the AS environment uses an OPC server to establish the connection, as presented in Figure 3. Setting up the OPC server software on the computer required configuring communication settings (PLC IP address, communication protocol, and port number) and adding the desired PLC tags/variables to the OPC server. The realistic behaviour of a DT developed in AS can be attributed to the comprehensive pneumatic workshop offered within the software. This workshop facilitates the creation and simulation of complex pneumatic systems by providing an extensive library of pre-built components, accurate physics modelling, parameter customisation, and the ability to integrate with other domains such as electrical, hydraulic, and control systems. Detailed models of pneumatic systems can be created using the pneumatic workshop to accurately represent the real-world behaviour. The customisation of various parameters ensures that the digital twin closely matches the characteristics of the physical components. At the same time, powerful simulation and analysis tools enable the visualisation, issue detection, and optimisation of the system's performance. To have increased this project's complexity in the implementation of the virtual commissioning, the cylinder that lifts the robot chassis (U/D cylinder) was controlled in position because a pneumatic cylinder in a specific position is less usual than the simple extension and retraction control. It is assumed that the pressure drops across the piston are small compared with the supply pressure and may be neglected.