# Comparison of Multi-Tracked Running Gears in Terms of Obstacle Negotiation Capabilities
## 5 Discussion  
Based on the simulation results, the best obstacle-overcoming abilities of solution E were demonstrated, regardless of the obstacle, in four of the five adopted criteria (Table 6). Figure 16: Track modules’ position during log crossing simulation for (**a**) solution C and (**b**) solution E. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Solution**} & **Obstacle Overcoming** & **Track Slip at a** & **Maximum Pitching Angle of the** & **Maximum Pitching Angle Speed of** \\  & **Time [s]** & **Critical Moment** & **Platform Frame [Degrees]** & **the Platform Frame [Degrees/s]** \\ \hline A & 3.65 & 0.74 & 43 & 270 \\ B & 3.61 & 0.75 & 54 & 270 \\ C & 3.98 & 0.97 & 32 & 145 \\ D & 3.73 & 0.77 & 46 & 175 \\ E & 3.48 & 0.66 & 14 & 37 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Results of second test for log negotiation. Figure 15: Diagram of the maximum log diameters that can be overcome by solutions A to E (**a–e**). In Test I, solution D achieved equally good results in two of the three obstacles. By analyzing the subsequent phases of overcoming obstacles, it can be concluded that the kinematic structure of the track module connection significantly affected the ability to adapt to the terrain profile. The forces transferred from one module to another may contain directional components that increase the ground pressure supporting the system through the principle of counterweight, as seen in the multi-tracked double-joint solutions (D, E). In the case of the multi-tracked single-joint solutions (B, C), this connection leads to the transfer of additional loads related to the lifting of the second module, reducing the possibility of generating traction force. Therefore, higher ground traction is needed. The minimum ground shearing resistant angle for solution B to overcome a curb was 42 degrees, for solution E, it was 2,5 times less, with 17 degrees. By changing the kinematics of the UGV body's architecture, it is possible to increase its ability to overcome obstacles but also to drastically reduce it. Solution B did not perform better than the single-module solution (A) due to the small track spacing relative to the obstacle dimensions and the limiting joint kinematics. In the case of this solution, an appropriate angle restriction or active module pitch angle control might be beneficial to improve the obstacle negotiation performance. The single-joint Solution C still showed significant improvement in climbing on slopes and curbs, but unfortunately, its kinematics are highly unsuitable for overcoming a single object such as a log. The results of the measurements of the time to overcome obstacles showed an up to 5% difference. The best solutions allowed for saving a few percent, and in the case of the ditch, the shorter time was associated with the undesirable phenomenon of skidding. Significant differences between the solutions for each obstacle were visible in terms of the speed and deviation angles. The dimensions of lightweight UGVs mean that even on small objects--such as a curb--they achieve significant deviation angles of up to 57 degrees. These are highly undesirable values, and their rapid changes pose a threat to the UGV operation. Solution E performed best in terms of the pitching, reducing the pitch angle of the platform frame by even 70% compared to the classic solution (A) and allowing for its changes to be more than 7 times slower. This improves, among other things, the capability of teleoperation using images from cameras. This is clearly an advantage of solutions with a common long frame; however, in this case, it might be necessary to consider the limited possibility of obtaining a small turning radius. The simulation results indicated the occurrence of kinematic inconsistency, reducing the necessary driving forces in the most advantageous multi-tracked solutions during low-slip driving.