## 2 Related Work
The integration of virtual commissioning with digital twins allows for different implementation configurations, as illustrated in Figure 2.  
According to the authors of [45; 46], real commissioning combines a physical assembly system with a real control system, ensuring the direct validation of hardware and software integration. Mixed virtual commissioning integrates a virtual assembly system with a real control system, enabling the verification of control software in a digital environment before deployment in actual production. Hybrid commissioning utilizes a real assembly system alongside a virtual control system, facilitating logic testing and optimization without the need for a fully implemented control software. Constructive virtual commissioning represents a fully digitalized approach, where both the assembly system and control system are simulated, allowing for comprehensive analysis and optimization before physical implementation [47]. Figure 1: Comparison of traditional and virtual commissioning processes, illustrating how integrating virtual commissioning reduces testing time and accelerates system deployment. According to the authors of [48; 49], effective virtual commissioning relies on the comprehensive digitalization of engineering processes. A robust software platform must support system design; the creation of virtual models for machines, robotic applications, and material flow; and the development of control programs with virtual testing and validation, including PLC behaviour simulation [50; 51]. Available software solutions can be classified into two primary categories. Digital factory [52] software, such as Delmia, Tecnomatix Process Simulate, NX Mechatronics Concept Designer, and CIROS, is designed for comprehensive manufacturing process simulation. In contrast, automation software, including WinMOD, SIMIT, Simster, and FluidSIM, specializes in modelling and testing control systems in HiL and SiL environments. According to the authors of [10; 53], virtual commissioning is a crucial tool for validating cyber-physical systems and is increasingly used as a prerequisite for digital twin implementation. The behaviour model, as part of virtual commissioning, enables realistic simulation and testing of manufacturing systems, significantly reducing errors, shortening commissioning time, and optimizing control programs before physical implementation. According to the authors of [54; 55; 56], effective virtual commissioning depends on appropriate software tools that support digital twin simulation, logical behaviour modelling, PLC system emulation, and control program development. As shown in Table 1, these software solutions can be divided into four main categories. The first category includes digital twin simulation tools, such as NX Mechatronics Concept Designer, Tecnomatix Process Simulate, Tecnomatix Plant Simulation, ABB Robot Studio, and CIROS, which enable the precise validation of system design before physical implementation. The second category focuses on logical behaviour modelling of the digital twin, represented by WinMOD and SIMIT, supporting control algorithm testing in HiL and SiL environments. The third category consists of PLC emulators, including S7-PLC SIM and PLC SIM Advanced, which allow simulation of control unit behaviour without requiring physical  
Figure 2: Classification of commissioning approaches, illustrating actual, mixed virtual, hybrid, and constructive virtual commissioning, based on the combination of real and simulated assembly and control systems. hardware. The final category includes PLC programming software, such as Simatic Manager and TIA Portal, which enable early error detection in control software. According to the authors, integrating these software solutions reduces commissioning time, minimizes testing costs, and enhances the reliability of manufacturing processes, ultimately improving overall system efficiency. Recent advancements in DT design for VC focus on hybrid modelling, cloud-based solutions, and AI-driven automation. [PERSON] et al.