# Remote-Controlled Method with Force and Visual Assists Based on Time to Collision for Mobile Robot
## 4 Experiment
### Experimental Results  
The experiments included three different results:  
* Time from start to finish;
* Number of times translational velocity fell below 0.0 m/s;
* Number of collisions.  
The time from start to finish and the number of times translational velocity fell below 0.0 m/s evaluated the operability. In addition, the number of collisions estimated the safety performance. The number of times the translational velocity fell below 0.0 m/s indicated the back operation of the mobile robot. The improvement in operability can be confirmed if the time from start to finish is short. In addition, if the number of times the translational velocity fell below 0.0 m/s is less, this indicates improvement in operability. If the number of collisions is low, the safety performance can be considered to have improved.  
As shown in Figures 12-14, the experimental results, which include all the subjects' results, are expressed. Figure 12 shows the time from start to finish. Figure 13 shows the number of times the translational velocity fell below 0.0 m/s. Figure 14 shows the number of collisions. In this study, a paired \(t\)-test was conducted for the experimental results. In Figure 12, \(*\) indicates that there is a statistically significant difference and a significance of \(p<0.05\). In Figures 12-14, the distribution of data is expressed by the error bars, and a significant difference over the factor environment or support is indicated by the horizontal bars.  
Figure 15, respectively. Similarly, the experimental results of the velocity, force commands, and time to collision for Case 4 are shown in Figures 19-21.  
As shown in Figures 16-18, _Pattern1_ of the force assist in Case 3 was generated at Area1 and Area2 when the TTC was lower than \(T_{th}\). The translational and angular velocity commands of Case 3 were changed because of the force assist. Hence, as shown in Figure 15, the trajectory of Case 3 is curved more deeply to the right side than the trajectory of Case 4 against the obstacle on the left side at Area1 and Area2. At Area3, _Pattern2_ of the force assist was applied to the control device before arriving at the goal position, and the mobile robot was operated in back operation. The high presence of the force assist caused the back operation at Area4 in Figure 15. In contrast, as shown in Figures 19-21, _Pattern1_ of the force assist of Case 4 was generated at Area3 when the TTC was lower than \(T_{th}\). The angular velocity command of Case 4 changed because of the force assist, whereas the translational velocity command was not modified. Hence, as shown in Figure 15, the trajectory of Case 4 is positioned closer to the goal position than the Case 3 trajectory at Area3. Around the goal position, the mobile robot in Case 4 could finish the course without back operation compared to the Case 3 trajectory.  
Figure 17: Experimental results of force commands of Case 3 for Subject A.  
Figure 18: Experimental results of time to collision of Case 3 for Subject A.  
compared to Case 2. In addition, safe performance was achieved in Case 4 compared to Case 2.  
Therefore, the method proposed for Case 4 was found to have improved the operability and safety performance, when compared to the methods proposed for Case 2 and Case 3. The authentication of the proposed method was confirmed.