## 4 Results and Discussion  
In this study, the PSO-based optimizers were designed for adjusting the parameters of the PID controllers to improve the route-tracking performance of the AGV and adjusting the parameters of the DC/DC converters to consume minimum power from the fuel cell while increasing the route-tracking performance. The studies carried out in this study were carried out in a simulation environment using the MATLAB/Simulink program licensed by the University of Illinois at Chicago (UIC). Tests were carried out for different reference routes by combining AGV, DC/DC converters, motors and fuel cell models created in the simulation environment. The purpose of this stage was to optimize controllers and converters in terms of performance by determining the optimal parameters. Then, a different reference route was applied to the combined model with the best performance, \begin{table}
\begin{tabular}{l l l l l} \hline \hline
**(i = 1, 2, 3, 4)** & \(\mathbf{K}_{\mathbf{l_{\mathrm{ac}}}}\) & \(\mathbf{L}_{\mathbf{i}}\) **(H)** & \(\mathbf{C}_{\mathbf{i}}\) **(F)** & \(\mathbf{R}_{\mathbf{i}}\) **(\(\boldsymbol{\Omega}\))** \\ \hline Maximum limit & 50 & \(100\times 10^{-6}\) & \(1000\times 10^{-6}\) & **100** \\ Minimum limit & 0 & \(1\times 10^{-6}\) & \(1\times 10^{-6}\) & **1** \\ \hline \hline \end{tabular}
\end{table} 
Table 6: The limits values of parameters of integral controllers and DC/DC converters’ components for Optimizer -2. Figure 6: PSO-based integral (I) controllers’ tuning block diagram of DC/DC converter optimization. and route tracking, power consumption, converter voltage-tracking and fuel-consumption performance were analyzed. As mentioned, Optimizer-1 uses the AGV's actual and reference positions for minimizing the route-tracking errors with the optimal parameters of four PID controllers, and Optimizer-2 uses the actual motor voltages (output voltage of the DC/DC converters); reference motor voltages, which are generated by the PID controllers; and the power consumption from the fuel cell. In order to determine these optimal parameters, a reference trajectory was applied to the system. Optimal values obtained as a result of this reference trajectory were also tested on another reference trajectory, and the most suitable optimal values were sought for different situations. The reference trajectory applied to determine the optimal values in the first stage is shown in Figure 7a. As can be seen in the figure, the trajectory to be followed for parameter optimization was chosen as a combination of both rotational and translational movements. The main reason for this was to determine the optimal parameters that ensure both movements of the AGV successfully and reduce power consumption while performing path tracking. The optimal values calculated with this trajectory are shown in Tables 7 and 8. Table 7 shows 12 PID controller parameters determined by Optimizer-1 to follow this reference trajectory with minimum tracking error and minimum power consumption. \begin{table}
\begin{tabular}{l l l l l l} \hline \hline
**K\({}_{\mathbf{P_{1}}}\)** & **K\({}_{\mathbf{I_{1}}}\)** & **K\({}_{\mathbf{D_{1}}}\)** & **K\({}_{\mathbf{P_{2}}}\)** & **K\({}_{\mathbf{I_{2}}}\)** & **K\({}_{\mathbf{D_{2}}}\)** \\ \hline
667.91830 & 3043.41076 & 6.99876 & 1907.50583 & 3154.132757 & 16.63205 \\
**K\({}_{\mathbf{P_{3}}}\)** & **K\({}_{\mathbf{I_{3}}}\)** & **K\({}_{\mathbf{D_{3}}}\)** & **K\({}_{\mathbf{P_{4}}}\)** & **K\({}_{\mathbf{I_{4}}}\)** & **K\({}_{\mathbf{D_{4}}}\)** \\ \hline
7500 & 1 & 25 & 3498.62756 & 5000 & 8.10674 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: The values of PID controllers’ parameters optimized by Optimizer -1.