## 3 Results
### Simulator Hardware of VR Systems  
This section details the hardware used in the different systems to interact with the VR environments. These differ from one study to another, as shown in Table 1. Most studies, 20 out of 28, developed a VR system for powered WUs and thus used a joystick to conduct navigation [28; 29; 30; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47; 48]. These varied from a real powered wheelchair joystick to an adapted gaming joystick. Furthermore, some of the studies that used a joystick also had training groups using alternative ways to drive the simulation, such as eye-trackers [28; 45] and BCI caps [49]. For manual WUs to drive the VR simulation, on the other hand, sensors attached to the wheels can be used, such as what was done by [PERSON] et al. [27] who placed VIVE trackers on the wheels to drive the simulation in VR; alternatively, the wheelchair can be placed on a platform that translates the movements of the wheel to the VR environment, such as the miWe simulator [50]. Regardless of the interaction method used in the variousstudies, each study took into account their end-user's motor abilities to determine the VR interaction method. \begin{table}
\begin{tabular}{p{128.0 pt} p{128.0 pt} p{128.0 pt}} \hline \hline
**Study** & \multicolumn{2}{c}{**Simulator Used**} \\ \hline [PERSON] et al. [42] & \(\bullet\) & The Microsoft Xbox One controller was used with a real joystick fitted on top of it. Spectra XTR2 rear wheel drive wheelchair for real life driving. \\ \hline [PERSON] et al. [45] & \(\bullet\) & The navigation was enabled by adapted joysticks, contactors and eye-trackers, all connected to the computer used for training. \\ \hline [PERSON] et al. [29] & \(\bullet\) & Two groups conducted the training using monitors, one using an Xbox controller with a regular desktop and the other using Emotiv Epoc+ as a controller with a brain-computer interface (BCI) desktop. \\ \(\bullet\) & Two further groups used an HMD, one with an Xbox controller, and one with Emotiv Epoc+. \\ \hline [PERSON] et al. [33] & \(\bullet\) & A real PW joystick. \\ \hline [PERSON] et al. [37] & \(\bullet\) & The user is sitting on a real wheelchair placed on a mechanical simulation platform, which drives the VR environment. \\ \(\bullet\) & The user navigates in VR with a joystick. \\ \hline [PERSON] et al. [47] & \(\bullet\) & A real wheelchair joystick: the VR2 with haptic feedback was used. \\ \hline [PERSON] et al. [28] & \(\bullet\) & One group used a real EPW with a joystick for movement in a HMD, another group used an EPW with eye-tracker for movement in VR which was shown on a LCD display. \\ \hline [PERSON] et al. [48] & \(\bullet\) & A gaming joystick was used, connected to the monitor through a USB cable. \\ \hline [PERSON] et al. [30] & \(\bullet\) & WUs remained seated in their own wheelchairs, but used a given wheelchair joystick for navigation. \\ \(\bullet\) & Clinicians sat on an office chair at a desk and used the same joystick. \\ \hline [PERSON] \& [PERSON] [36] & \(\bullet\) & Xbox controllers to control the VR environment. \\ \(\bullet\) & A real wheelchair for the MR group. \\ \hline [PERSON] et al. [27] & \(\bullet\) & The user sat on a wheelchair in a stationary position; HTC VIVE trackers were placed on the wheels to replicate movements in VR. \\ \hline [PERSON] et al. [49] & \(\bullet\) & BCI cap \\ \hline [PERSON] et al. [39] & \(\bullet\) & Quickie Salesa M2 power wheelchair \\ \hline [PERSON] \& [PERSON] [50] & \(\bullet\) & miWe simulator Own manual wheelchair \\ \hline [PERSON] \& [PERSON] [51] & \(\bullet\) & miWe Own manual wheelchair \\ \hline [PERSON] et al. [52] & \(\bullet\) & Own manual wheelchair Wheelchair ergometer \\ \hline [PERSON] et al. [53] & \(\bullet\) & Simulation platform Manual wheelchair \\ \hline [PERSON] \& [PERSON] [54] & \(\bullet\) & Wheelchair ergometer EON IcubeTM Mobile \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Simulator hardware of VR system. Similar results were found by [PERSON] et al. [PERSON] et al.