# Engineering Method and Tool for the Complete Virtual Commissioning of Robotic Cells
## 2 Related Work  
Since traditional commissioning is proven to be time- and cost-consuming, many authors have thoroughly investigated VC technology during the last few years. The VC is a technique that aims to validate the control software of a manufacturing system with a simulation model, in a virtual environment and in an early stage of its commissioning process [22; 23]. A great advantage supported by the VC is that many design activities can be parallelized. This makes it possible for different engineers to work together simultaneously, reducing the designing time [24]. Additionally, it allows for possible errors to be detected and corrected, improving the performance of the entire robotic cell prior to its installation [25; 26; 27]. A determining factor for an efficient VC is its capability to combine technologies from different engineering fields so as to create a holistic environment where all the aspects of the manufacturing systems are considered at the same time [28; 29]. Despite some recent advances, a severe absence of integrated simulation-based platforms can be noted in the standard industrial practice [24]. Digital plant models still divide the geometry and physics of the system from the PLC control program and signals, which are tested within the control software development tool (i.e., without a direct vision of the process behavior). Alternatively, by exploiting the open platform communications (OPC) protocol, the real PLC system can be connected with a 3D virtual model of the cell, defined in DELMIA or Dymola environments, as in [30; 31]. An example of OPC coupling, realized through the WINMOD and SIMIT packages, can be seen in [18; 32], but it is limited to the Siemens platform, while open IEC-61131 PLC programs should also be emulated. Some software producers are heading towards the development of a single application that includes both devices' kinematic and PLC program simulations. In [33], a manufacturing cell was simulated using Process Simulate, namely a specialized software that is part of Siemens Tecnomatix suite and offers a 3D modeling environment where the user can test the connection between mechatronic devices and a PLC. Similarly, Simumatik3D was employed in [25] to model a didactic robotic cell for a pick and place purpose and to test the related PLC control program. A relevant improvement provided by this software (compared to Process Simulate) is that PLCs of any vendor can be simulated. A common disadvantage, instead, regards their relatively poor robot simulation capabilities. In fact, robot movements can only be approximated since there is no real virtual controller running on the application, only a generic emulator. From the literature review, it emerges that one of the main limitations of VC solutions for robotic cells is related to the scarce realism of the simulated automated plant. Therefore, the only viable strategy for achieving highly reliable models seems to be the integration of dedicated commercial platforms [32; 34]. Multi-software frameworks have been widely investigated by academic researchers in recent years, and not only regarding VC. They have been employed, e.g., for the design of servo-actuated mechanisms [12; 35; 36], the dynamic characterization of robotic systems [37], and for the tuning of robot controllers [38]. In this context, the main objective of this work is to develop and test a novel VC tool that leverages the integration between RS and TC. Since the software TC turns a PC into a real-time controller, the proposed approach can be utilized to either:  
* Test a real PLC system, i.e., realizing the so-called hybrid commissioning as a part of the hardware-in-the-loop approach;
* Simulate its behavior on a standard PC, i.e., realizing a full VC with a software-in-the-loop approach. The PLC programs are tested in RS, where exact copies of the ABB controller and settings are available, obtaining extremely accurate robot replicas.