# A Semi-Automatic Wheelchair with Navigation Based on Virtual-Real 2D Grid Maps and EEG Signals
## 3 Results and Discussion
### Wheelchair Movement to Reach Map-Based Desired Target
In particular, in this case, the wheelchair determined it position on the grid map at the coordinate A(5,0) and the direction of the wheelchair \(d\) is Up. In the semi-automatic wheelchair, people with disabilities can control the wheelchair using EEG signals to select one of the commands on the interface screen with one sign corresponding to the target C(0,5). With the starting point A(5,0) and the target point C(0.5) selected, the RL model will produce a sequence of control commands for the path and then these commands are converted to control commands in the real environment for the wheelchair using Equations (8a)-(8d) as shown in Table 4.  
Figure 14: Representation of the simulation route using the semi-automatic control and the wheelchair’s real path (**a**) The blue arrow route simulated using DQNs; (**b**) the wheelchair movement path in the real environment using DQNs and the reference path. Figure 13: The real path of the wheelchair movement and the reference path. In addition, in this experiment, the actual path of the wheelchair with the proposed method of DQNs (blue path) is compared with the standard path (green dashed path), as shown in Figure 14b, for evaluating the wheelchair movement path and the simulated path. The results showed that the wheelchair could move to reach the desired target with the average error of \(\pm\)0.2 m in the \(X\) axis and \(\pm\)0.2 m in the \(Y\) axis. The purpose of these experiments is to compare the results of the semi-automatic control using the RL method with the self-control by the user using the EEG signals. In particular, Figure 15a shows three graphs which represent the wheelchair movements, in which the blue path is that of the proposed mode and the red path is that of the self-control mode. From Figure 15a, it can be seen that the wheelchair's path when controlled by the semi-automatic control method is closer to the reference path than when using the self-control method. In addition, the wheelchair path using the semi-automatic control is smoother and more continuous than the path using the self-control. To clarify the two control methods, we recorded the wheelchair control commands during the movement to reach the destination. In Figure 15b, the control commands are shown on the vertical axis with the values of \(-\)2, 0, 1, 2 corresponding to the commands to turn left, stop, go straight, and turn right. Therefore, it could be seen that the wheelchair moved with high stability in the case of the semi-automatic control with different movement environments compared to the mode of the self-control user. In addition, the result showed that the automatic control user mode spends less time on wheelchair movement with the average of about 80 s compared to that of the self-control user with the average time of about 95 s. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**State of** & **Current Direction** & **Action of Model** & **New Direction** & **Action of** \\
**Wheelchair** & \(\mathbf{D}\) & \(\mathbf{A}\) & \(\mathbf{d}^{\prime}\) & **Wheelchair \(\mathbf{a}_{W}\)** \\ \hline (5,0) to (4,0) & Up & Up & Up & Forward \\ (4,0) to (3,0) & Up & Up & Up & Forward \\ (3,0) to (2,0) & Up & Up & Up & Forward \\ (2,0) to (1,0) & Up & Up & Up & Forward \\ (1,0) to (1,1) & Up & Right & Right & Right–Forward \\ (1,1) to (1,2) & Right & Right & Right & Forward \\ (1,2) to (1,3) & Right & Right & Right & Forward \\ (1,3) to (1,4) & Right & Right & Right & Forward \\ (1,4) to (1,5) & Right & Right & Right & Forward \\ (1,5) to (0,5) & Right & Up & Up & Left–Forward \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Wheelchair Control Commands Converted from Simulation Commands. Figure 15: The comparison of the stable movements of the wheelchair in two control methods (semi-automatic control and self-control). (**a**) The real paths of the two control methods and the reference path; (**b**) the control sequences of the two control methods.