*4.2. VR Model*

According to the proposed approach, the real scenario is created in virtual reality to visualize the designed process and to evaluate this layout, for instance, in terms of the robots working range, among others. Figure 7 shows the creation of the virtual reality environment: Figure 7a is the original area of the facilities, Figure 7b is the 3D point cloud resulting from scanning this area with *FARO Focus3D X130 HDR*, and Figure 7c is the *Blender*-resulting virtual environment ready for its use in virtual reality. The VR model is completed adding the virtual model of all the components of the cell (robots, conveyor belt, tables, parts, etc.). Finally, the physical behavior of the elements and the human interaction is implemented using *Unity3D*. The final result is shown in Figures 8 and 9, where the high quality of the 3D reconstruction to create the immersive effect in the VR interface can be noticed.

**Figure 7.** From the real to the virtual environment: (**a**) real environment, (**b**) 3D point cloud, and (**c**) virtual environment.

**Figure 8.** General view of the virtual cell.

**Figure 9.** Virtual cell: (**a**) containers with the parts and assembly robot, and (**b**) delivery robot.

Using this virtual scenario, the process has been simulated and evaluated for the virtual commissioning via applying lean automation concepts and verifying that the design fulfills the requirements. Different work models were defined, assuming a distribution of tasks between the operator and the collaborative robots. Each of these models was mainly characterized by the layout, the logic of behavior, and the parameters associated with production management. The manual process without robots was also evaluated. After analyzing and comparing the models in terms of (1) efficiency and optimization, (2) reduction of movements and transportation, and (3) possibility of future extensions, these are the main conclusions which validate the designed process (including elements, layout, flowchart, etc.):

	- The parts are inspected previously to the assembly of the covers, avoiding spending time and wasting materials on wrong parts.
	- The operator receives instructions to continue his/her tasks in parallel with robot's tasks. It is not necessary to wait.
	- The buffer avoids bottlenecks.
	- The robot discards automatically the wrong parts. The operator does not have to wait for the inspection result.
	- If a part is pending, it is requested at the end of the batch, increasing process flexibility and avoiding confusions to the operator.
	- If all the tasks are done manually without any automation, the operator will spend time in repetitive tasks, the inspection will be subjective, and materials will be wasted, among other inefficiencies. Thus, it will not be the optimal situation.
	- Containers and trays are close to the operator in order to reduce movements.
	- The conveyor belt permits the transportation of the completed batches from the assembly area to the delivery area, avoiding the use of a mobile platform or an automatic guided vehicle (AGV).
	- New workstations can be added.
	- Augmented reality can be used as HMI instead of the current screen. For this purpose, it is necessary to locate QR-codes in the real scenario. Their possible location has been studied in the virtual scenario as it can be appreciated in Figure 9a.

Once the process and the layout have been validated in the virtual space, they are physically implemented in the real scenario, as shown in Figure 10. Comparing Figures 8 and 10, the high

accurate 3D reconstruction to create the immersive effect in the VR interface can be noticed. The virtual environment is totally accurate to the real one, including the minimum details (real dimensions, textures, colors, lighting effects, etc.) to transmit to the user the sense of presence. Furthermore, Figures 11 and 12 show the elements in detail.

**Figure 10.** General view of the real scenario.

**Figure 11.** Detailed view of the collaborative area (real scenario).

**Figure 12.** Detailed view of the use case components: (**a**) parts in the containers, (**b**) covers, (**c**) buffer, (**d**) empty tray, (**e**) parts in a tray, and (**f**) completed batch.
