## 3 Materials and Methods  
The development workflow of the case study DT application for a 3 DoF cylindrical robot type (or RPP robot, which contains three linkages and three joints--one revolute joint that rotates about the base, and two prismatic joints), as presented in Figure 3, is based on three main elements: (1) 3D asset creation; (2) DT and VC application development--the ecosystem around AS; and (3) DT and MR application development--the ecosystem around Unity. The interactions between architectural components, physical and cyber layers, are a part of the DT approach and are realised through the OPC approach, which is usually used in horizontal and vertical communication automation processes because it provides semantic interoperability for all layers.  
Figure 3: The development workflow of the project.  
For activities requiring repetitive, accurate motions in a constrained environment, such as pick-and-place operations, assembly tasks, or simple welding tasks, a 3 DoF pneumatic cylindrical robot is well suited. The RPP configuration implies that the robot has one revolute joint followed by two prismatic joints. In a pneumatic cylindrical robot, all movements are executed through pneumatic actuators. These actuators convert compressed air into mechanical energy, providing a fast and responsive actuation method. The robot's joints are powered by these actuators, allowing it to perform various tasks within its cylindrical workspace. This robot, as depicted in Figure 4a, is an educational setup from Tech-Con Lab--Department of Automatic Control and Applied Informatics from TUIASI--and used by students to learn about the principles and operation of pneumatic systems, control algorithms, and robotic kinematics.  
The following pneumatic actuators power the robot's joints:  
1. Revolute joint (R): a pneumatic rotary actuator--called L/R--(model ARP 055) is used to execute the rotation of the base joint. It allows the robot arm to rotate horizontally at a maximum of 90\({}^{\circ}\), panning within the cylindrical workspace;
2. Prismatic joint 1 (P1): a pneumatic linear actuator used to control the vertical motion of the robot arm--is called U/D. This actuator extends or retracts to raise or lower the arm within the workspace. The model is 41M2P080A0200, a magnetic double action cylinder with O80 mm and 200 mm strokes.
3. Prismatic joint 2 (P2): another pneumatic cylinder used to control the robot arm's radial motion is F/B. This actuator extends or retracts to adjust the robot's reach within the cylindrical space. The model is 60M6L063A040, a magnetic bidirectional cylinder with O63 mm and 400 mm stroke. It is a bidirectional cylinder because one end contains EOAT--180\({}^{\circ}\) angular gripper model CGSN-25 and the other has a counterweight to ensure smooth movement.  
The control device for the robot is implemented with a PLC model XBC-DR30 SU, which is a compact PLC offering a variety of input and output (I/O) options and communication capabilities. The PLC receives input signals from various sensors (inductive limit  
Figure 4: The real RPP robot configuration: (**a**) the real 3 DoF pneumatic robot; (**b**) the pneumatic circuit diagram of the robot; and (**c**) the PLC of the robot.  
switches for L/R pneumatic rotary actuator and gripper, ultrasonic sensors for the U/D cylinder and magnetic sensors for the F/B cylinder). The PLC sends output signals to the solenoid valves with electric commands and the external servo pilot, causing the robot's joints to move and perform the desired tasks. The rotary actuator uses a bistable valve 5/3 with a central position closed model 338D-015-02 with coils voltage of 24 V DC--which receives the command directly from the PLC output. For the F/B cylinder and gripper valves, monostable solenoid valves 5/2 model 358-015 are used. Control in position for the U/D cylinder is necessary to use a valve 2X3/2 NC model 338D-015-02 and a proportional solenoid valve 2/2 way NC model 21A2 KCV15-10 connected to a controller +Smart.