# Leveraging Digital Twin Technology for Enhanced Cybersecurity in Cyber-Physical Production Systems
## 4 Case Study
### Human-Robot Collaborative Assembly System  
In this study, we employed an HRC assembly system, which involves humans and robots performing concurrent tasks within a shared space. This setup underscores the imperative of robust cybersecurity measures to safeguard human workers from potential harm resulting from compromised robot operations [60].  
The HRC assembly system comprises three workstations: a tool-changing station, an _ABB IRB 2600-20(12)/1.65_ robot with a PLC gripper, and a conveyor. The system's layout is depicted in Figure 7, while Figure 8 illustrates the physical arrangement of these components. Human operators interact with the robot across these workstations, monitored by cameras (_Microsoft Kinect_) for planning and scheduling the assembly process. Various systems facilitate data flow and command transmission between workstations and the robot: a _UnitController_ for assembly data analysis and command issuance, a _Cockpit_ for process planning, a _CollisionAvoidance_ system for analyzing human-robot movement, and a _WorkerIdentification_ system for tracking worker movements.  
We refined our reference model by gathering data from three primary sources: outputs from the _SYMBIO-TIC_ project, a field study at the ASSAR venue, and interviews with former _SYMBIO-TIC_ project participants. More detailed insights into the HRC system can be found in the [61] project, especially the third demonstration at the ASSAR Industrial Innovation Arena in Sweden. The digital-twin model for HRC is presented in Figure 9.  
The _WorkerIdentification_ and _UnitController_ systems independently evaluate the positions and availability of workers and the robot. Utilizing these data, the _Cockpit_ system orchestrates the assembly process planning and scheduling for product batches, subsequently relaying these plans to the _UnitController_. The _UnitController_ then gathers detailed assembly operation instructions, such as robot movements from graphical robot programming software (e.g., [62]) and gripper commands from robot simulation software (e.g., [63]).  
These instructions are converted into executable codes and I/O signals by the _UnitController_, directing both the robot's actions via controllers (e.g., IRC [64]) and the gripper's operations through PLC.  
Furthermore, the _UnitController_ communicates task instructions to workers and workstations via the _HMIC_, typically accessed through mobile devices. To enhance the HRC system's resilience, assembly process data are duplicated and synchronized across the _UnitController_, _CollisionAvoidance_, and _Cockpit_ systems. The _CollisionAvoidance_ system, upon detecting potential human-robot collisions, adjusts the robot's trajectory and communicates updated instructions to the _UnitController_ to prevent accidents.  
Figure 8: Physical setup of HRC assembly workstations.  
Figure 7: Layout of HRC assembly workstations.  
Simulation and programming tools such as _RobotStudio_, _Drag&Bot_, and others are consolidated within a workstation running _Windows 10_ for \(\times\)64 systems, as shown in Figure 9. The _CollisionAvoidance_ operates on a separate _Windows 10_ workstation, while _WorkerIdentification_ runs on another _Windows 10_ computer. _HMIC_ applications are hosted on Android devices. Among these software components, only _Drag&Bot_ supports direct remote access. Others, like _Cockpit_, are encapsulated in software containers (e.g., doc [65]) to enhance security and minimize data exposure risks, with strict process communication, memory allocation controls, and role-based access policies.  
The network, protected by a password, employs an _ASUS_ router with SSH encryption and software firewalls for IP-specific connections, ensuring secure communication and service connectivity.