# A Mobile Robot with Omnidirectional Tracks--Design and Experimental Research
## 4 Discussion  
The paper presents a solution for a robot equipped with completely overlapping multidirectional tracks with a symmetrical roller position. A light robot prototype was designed and constructed using additive manufacturing technology to be later used in experimental research on a specially constructed test measurement bench. The robot's parameters were examined along the longitudinal and transverse axes.  
The experimental research without ride direction correction confirmed the occurrence of the effect of motion trajectory deviation during transverse motion. Similar effects of the trajectory curve were observed during the simulation tests of the robot with non-overlapping tracks [27] and with partly overlapping tracks [24].  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{2}{c}{**Longitudinal Motion**} & \multicolumn{2}{c}{**Transverse Motion**} \\ \hline
**Ride without** & **Ride with Direction** & **Ride without** & **Ride with Direction** \\
**Direction Correction** & **Correction** & **Direction Correction** & **Correction** \\ \hline \(\Delta\alpha\) = 0.085 rad & \(\Delta\alpha\) = 0.025 rad & \(\Delta\alpha\) = 0.549 rad & \(\Delta\alpha\) = 0.207 rad \\ \(\Delta v_{\rm i}<0.02\) m/s & \(\Delta v_{\rm i}<0.02\) m/s & \(\Delta v_{\rm i}<0.03\) m/s & \(\Delta v_{\rm i}<0.04\) m/s \\ \(\omega_{R}=0.009\) rad/s & \(\omega_{R}=0.003\) rad/s & \(\omega_{R}=0.052\) rad/s & \(\omega_{R}=0.024\) rad/s \\ \hline \hline \end{tabular}
\end{table}
Table 2: Comparison of the conducted measurement results based on the distance of 0.7 m for the transverse motion, and 1.2 m for the longitudinal motion.  
The data quoted in the references indicate a 3.8% deviation between the theoretical speed and the one obtained in the dynamic simulation during transverse motion, and less than a 1% deviation in the main motion. In these references, no quantitative data was presented regarding the change in the angular orientation of the robot.  
The data obtained during the conducted experiment showed a deviation increment of 0.016 rad/s in the longitudinal motion, and 0.133 rad/s in the transverse motion.  
Such significant values of the trajectory curve probably result from the mechanical imperfections of the prototype, which were probably due to the adopted drive system's structure without idling rolls and the used manufacturing technology. The fact that the track links and rollers were made of TPU filament, were of 40D hardness in the Shor scale, and had a low friction coefficient resulted in low adhesion of the robot to the surface. It was shown that this effect could be corrected using a suitable control system. The proposed static method of ride direction correction performed this role. The application of the continuous track speed correction allowed the angular deviation during longitudinal motion to be reduced to 0.007 rad/s, and to 0.019 rad/s during transverse motion. Despite the used correction by a value smaller than would result from the transverse motion calculations, a significant improvement in trajectory parameters was observed. This confirms the correctness of the used method and creates opportunities for further research and experiments.  
The downside of the used correction method is the fact that it is a static method, which means that it requires earlier experimental tests of a robot on a particular type of surface, with the results needing to be used as the basis for the determination of efficient correction parameters. The application of a dynamic method of ride direction correction would improve the performance even more, and, in effect, eliminate the consequences of deviations in trajectory during robot motion. In further research stages, the prototype will be equipped with additional body orientation angle measurement sensors, which will allow the use of dynamic motion direction correction.