## 3 Results and Discussion
### Simulating the Physical Ergonomic Conditions of Assembly Procedures in VR and DHM
#### 3.1.2 Simulating Physical Ergonomics Analysis  
After completing all the scenarios, various simulations were run to analyze the worker's postures and other ergonomic conditions while executing the task in the workplace. These simulations included all the worker's tasks, such as accessibility, reaching and manipulating things, gripping, and picking up tools and parts during the assembly procedure. VR provided a good comprehension of tasks from the perspective of the worker, allowing for an immersive interaction. It was feasible, for example, to walk around the vehicle in production and imagine different ways to carry out duties, obtaining a clear understanding of the worker's difficulty in performing the assembly procedures. DHM simulations were performed with Jack to provide measurable data for postural analysis, an available resource that was used to complement VR analyses. The digital human model in Jack is made up of various elements. The Jack human library contains a large number of default models. Depending on the percentile population, each default human figure has some default segment lengths (e.g., 95 th, 50 th, or 5 th percentile) [9]. The automotive industry set the 50 th percentile female as the default for most factories worldwide. The percentile was calculated using statistical assessments of its plants' populations over the world (except for Asians). According to the assessment, the manikins' dimensions (Figure 12) are sufficient to accommodate 90 percent of this industry's workers [9]. To evaluate specific tasks, like hand clearance and strength, we used percentile 95 th male. The selection of the 50 th percentile female and 95 th percentile male models was based on an extensive internal anthropometric study conducted by a large automotive company over 10 years; the company concluded that these percentiles adequately represent approximately 90% of their operational workforce. However, we acknowledge that this approach does not fully capture the diversity of the workforce, especially regarding populations with distinct anthropometric profiles, indicating the need for complementary studies or more inclusive models. This limitation underscores the need for complementary studies or the development of more inclusive models, as discussed in Section 4. The first virtual simulation was related to the installation of the Front Transmission Axle, where [PERSON] began using the DHM for pre-torque analysis, one of the most ergonomically critical tasks of this assembly procedure. This simulation (Figure 13) shows that the worker is unable to access the screw head to perform pre-torque, a manual task, indicating that the assembly procedures do not meet a minimum hand clearance requirement. Figure 12: Jack manikins [9]. All simulations are shown alongside photographs from the physical assembly procedures, to make it easier to compare the methods. Teconomatix reproduced the identical assembly procedure in VR. Figure 14 illustrates that the interface condition between the driveshaft and gearbox does not allow for manual pre-torque because the back of the hand will touch the gearbox, limiting finger access to the screws. Every manual task must give sufficient hand access around all parts or tools required to accomplish the assembly procedure properly [9]. The clearance required for the 95 th percentile male wearing production gloves of 1.5 mm in thickness is shown in Figure 15.  
Figure 14: Hand clearance simulation (immersive). Figure 13: Hand clearance simulation (non-immersive). Figure 15: Hand clearance requirements [22]. The DHM Rear Driveshaft assembly procedure was simulated. Figure 16 shows an analysis of wrist posture during a torque application task that indicates evidence of an extreme radial wrist deviation of 38.7 degrees on a scale ranging from \(-45\) to \(45\) degrees. Figure 17 illustrates the hand/wrist-posture scale adapted from a general ergonomics industry guideline [23].