# Supervision System 4.0 for a Road Tanker Washing Robot Manipulator
## 1 Introduction
One of the advantages of integrating SCADA with CPSs is the ability to simulate the operation of a real system with a DT [11]. The availability of a DT that matches the physical process allows the functionalities of the SCADA system to be tested at the same time as the mechanical design, production and installation phases are being developed. This allows to reduce the development time of new systems and to validate their operation before they are produced [12; 13]. In addition, a DT allows new operation cycles to be tested without the need to stop the physical system operation or even testing the system's responses in the event of a failure or malfunction. In addition to allowing testing of the control logic, a DT is also useful for testing the supervision interfaces and the communication between different systems. For instance, operators can visualize the response to their actions through the DT, while testing the HMI interface of the SCADA system. Supervision interfaces can then be improved based on the users' feedback, thus reducing the adaptation period when the supervision system is implemented. Finally, DTs can also be used to assess the risk of occupational injuries and accidents to human workers in industrial workplaces [14]. In recent years, increasing attention has been paid to creating DTs for gantries and other types of robotic manipulators. For instance, in [15], the authors developed a DT for a gantry robot used in automated wood furniture production. The DT was used to simulate robot trajectories and aid in the planning of efficient and collision-free robot trajectories, using the NavMesh algorithm. In [16], a DT was developed for a multigantry system used in the ship building industry to manipulate hull parts. The simulation capabilities of the DT were used to optimize resource allocation in real time during production. A DT of a knuckle boom crane is presented in [17]. In that work, stress analysis is carried out in the DT to perform condition monitoring of the real system. For this purpose, the authors resort to a finite element model which is validated against a physical prototype. In contrast to the previously mentioned works, this paper focuses on the integration of a DT into a SCADA system and the use of the DT to validate the SCADA services. Nowadays, in the tank cleaning industry, the washing of road tanker trucks is done manually, with professionals positioning (manually) the washing system at the man entrance. Operators often must enter the road tanker truck to carry out difficult cleanings (often with toxic products), thus being exposed to the risks associated with this work. The entire process is done without automatic supervision, and all activity, maintenance, faults and malfunctions are also recorded manually. For this reason, the work developed in this paper is of the utmost importance for road tanker cleaning companies (and their workers) seeking digital transformation and automatic washing, control and supervision systems. The SCADA system proposed in this paper (and in previous work [18]) manages the automatic washing of road tanker trucks, the control and supervision of the entire washing system and complies with some of the requirements of industry 4.0. Namely, the proposed SCADA system leads to the digital transformation of the entire washing process and supports supervision via Internet, the use of a Digital Twin for process simulation and optimization, machine-to-machine communication, incorporation of fault diagnosis and alarm management and automatic generation of reports. In this way, professionals in this sector benefit from greater safety at work and companies will be able to improve the efficiency of their washing processes, thus reducing costs. One of the goals of this work is to develop a SCADA system under the industry 4.0 principles. Specifically, the present work focuses on the application of these principles to supervise a new road tanker washing robot.