# Engineering Method and Tool for the Complete Virtual Commissioning of Robotic Cells
## 1 Introduction  
The current industry is characterized by increasing products complexity and personalization [1, 2]. Products evolve by integrating advanced capabilities of sensing, communicating and by reacting to changing situations with increasing levels of reasonings. Smart manufacturing, usually gathered under the Industry 4.0 umbrella, supports such a scenario providing a means to answer to always different product specifications maintaining a high process efficiency and economic competitiveness [3, 4, 5]. Manufacturing systems became more intelligent and autonomous due to the implementation of emerging communication, information and control technologies. Modern assets comprise advanced sensory apparatus, service-oriented computing platforms and modular controllers, integrating cyber-physical systems with high-fidelity simulation predictive models [6]. In particular, the ongoing factory digitalization has inevitably changed not only the manufacturing but also the way that products are designed and consumed [7]. Since modern markets continually demand flexible and customized products, development and commissioning processes are often very compressed [8]. Simulation and virtual prototyping technologies are consolidating their role in transferring testing and optimization activities in virtual environments, pursuing realism, easiness of use and reliability [9, 10, 11, 12]. Their application extends to the whole product life cycle [7, 13] as well as the related production systems. Nowadays, manufacturing plants require a higher adaptability, which is reached due to reconfigurable automation systems governed by advanced controllers, able to interpret operating scenarios and calculate and perform the optimal sequence of operations to achieve the best productivity and manufacturing quality in any condition. Thus, the control logics must embed the manufacturing knowledge and intelligence needed to interpret the surrounding environment and generate the optimal robust strategies. The programming of such intelligent robotic manufacturing has become increasingly complex and challenging, requiring a long time for verification and validation. Furthermore, it must be noted that modern robotic cells are governed by multiple controllers, namely at least a programmable logic controller (PLC) and a robot controller, whose control logics must be coordinated [14]. Therefore, from the initial design stages, the cells' offline development and debugging is usually performed via the use of virtual prototyping software (i.e., general-purpose computer-aided engineering or specific computer-aided robotics packages--see [15; 16])--where the layout of the cell, along with its behavior, can be modeled and simulated [17]. In these tools, the cell geometry, kinematic of robots and other devices, and the governing logic can be represented, including exchanged signals and sequences of commands to be executed. To obtain high-fidelity models, it is beneficial to include real hardware and/or software elements (e.g., commercial control units) in the virtual environment, which will be then become part of the implemented solution. These approaches, known as hardware-in-the-loop and software-in-the-loop [16; 18], respectively, are the bases for an effective virtual commissioning (VC) strategy for concurrent engineering problems [19]. They provide the capability of developing and testing complex plants before their implementation. In a mechatronic system, due to the large variety of involved devices, an efficient VC must connect different hardware and software elements, allowing for the use of the same interface and interaction modality for both the real and virtual counterparts. Current virtual prototyping solutions often suffer from limited interaction capabilities with other software/hardware devices available on the market [20]. Therefore, the need of interfacing tools enabling the communication between different components (following standards and architectures of industrial communication protocols) becomes crucial.