# Path Tracking of Agricultural Vehicles Based on 4 WIS-4 WID Structure and Fuzzy Control
## 4 Conclusions  
1. Based on the 4 WIS-4 WID structure and fuzzy control, a tracking model for low-speed agricultural vehicles is proposed so that the steering center is not limited to the left and right extension lines of the rear axle, thus enriching the form of vehicle movement and improving the path-tracking quality and convergence efficiency.
2. In a rectangular test area 25 m long and 18 m wide with the UWB module working as a positioning system, the steady-state deviation of the prototype vehicle ranged from 41 to 79 mm for straight-line path tracking, and the average deviation of the rectangular path was 185 mm in four initial states, which makes it feasible for driving on narrow roads in the facility.
3. The mechanical structure of the prototype vehicle fits with the size of internal roads and corners of most greenhouses in China. The path-tracking method could improve the intelligent performance of vehicles used in the greenhouse, providing more feasibility for future applications such as transporting materials and conducting mechanized operations.
4. Changes in temperature and shading in the greenhouse can affect positioning accuracy. The potential wheel side-slip phenomenon will also impact path-tracking accuracy. In subsequent research, the mechanical performance of the prototype vehicle needs to be improved, and the positioning accuracy of UWB in different environments needs  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Initial States**} & \multirow{2}{*}{**Tracking Model**} & \multicolumn{2}{c}{**Tracking Accuracy**} & \multicolumn{2}{c}{**Convergence Efficiency**} \\ \cline{3-6}  & & **Average** & **Steady-State** & **Stability** & **Settling Time/s** \\  & & **Deviation/mm** & **Deviation/mm** & **Distance/mm** & **Settling Time/s** \\ \hline \multirow{2}{*}{(1 m, 90\({}^{\circ}\))} & TPP & 620 & 50 & 3914 & 11.7 \\  & FCP & 169 & 46 & 2418 & 6.2 \\ \hline \multirow{2}{*}{(1 m, 0\({}^{\circ}\))} & TPP & 220 & 34 & 5332 & 14.4 \\  & FCP & 153 & 35 & 3052 & 8.6 \\ \hline \multirow{2}{*}{(1 m, \(-\)90\({}^{\circ}\))} & TPP & 277 & 39 & 4751 & 12.1 \\  & FCP & 212 & 36 & 2582 & 6.5 \\ \hline \multirow{2}{*}{(0 m, 90\({}^{\circ}\))} & TPP & 342 & 48 & 3966 & 11.3 \\  & FCP & 38 & 51 & 1661 & 4.4 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Statistics of the comparative tests.  
to be tested. In addition, the \(d\)-\(\theta\) diagram merits deepened research to achieve an ideal linear convergence effect, and also the negative correlation between the steering radius \(R\) and the integrated deviation \(\Delta\theta\).  
Conceptualization, L.X. and L.Y.; methodology, L.X., Q.C. and L.Y.; Data curation, L.W.; software Q.C.; writing, review and editing, L.X. and L.Y. All authors have read and agreed to the published version of the manuscript.  
This research was funded by Key R&D Program of Zhejiang, grant number 2022C02042.  
Not applicable.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.