## 3 Results and Discussion  
The heliostat and the RTU of the control system are shown in Figures 18 and 19. The RTU consists of the PCB (Printed Circuit Board) of the MCU and the PCBs of the motor driver circuits. It is powered by a 24 V power supply for the motor driver circuits, and it is regulated at 5 V and 3.3 V in order to provide the power to the RTU components. The developed GUI of the SU and the mobile App are shown in Figures 20 and 21. The GUI displays the values of time and date (date, local time, universal time, solar time, Julian day, day of the year, daylight saving time, and time zone), solar position (latitude and longitude, solar angles, declination, hour angle, right ascension, equation of time, dawn hour, sunset hour, solar noon, and daytime), heliostat data (latitude and longitude, heliostat angles, operation status, MAC address, an time and date), and the status of the communication with the RTU. There are also the control buttons and an image that shows the OS of the RTU. The mobile app consists of the buttons for the Bluetooth connection, labels that show the OS of the RTU, and the control buttons. The date and hour are colored in red if there is an error of one second in relation to the time of the device. Otherwise, the values are displayed in green. For both, the GUI and the mobile app, the control buttons are not activated until the communication with the RTU is established. Figure 16: Setpoint of the orientation control for the azimuth angle (**a**), the elevation angle (**b**), and both angles (**c**). Figure 17: Final reference error for the azimuth angle (**a**), the elevation angle (**b**), and both angles (**c**). Figure 19: Remote terminal unit. Figure 20: Graphical user interface. Figure 18: Heliostat. Figure 23: Orientation control response of the heliostat for the azimuth angle (**a**) and the elevation angle (**b**). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Setpoint**} & \multicolumn{2}{c}{**DC Motors**} & \multicolumn{2}{c}{**Heliostat**} \\ \cline{2-5}  & **Azimuth** & **Elevation** & **Azimuth** & **Elevation** \\ \hline Desired Ref & 0.05371\({}^{\circ}\) & 0.03761\({}^{\circ}\) & 0.09577\({}^{\circ}\) & 0.05401\({}^{\circ}\) \\ Discretized Ref & 0.02352\({}^{\circ}\) & 0.02730\({}^{\circ}\) & 0.08484\({}^{\circ}\) & 0.05568\({}^{\circ}\) \\ Final Ref & 0.0\({}^{\circ}\) & 0.0\({}^{\circ}\) & 0.08236\({}^{\circ}\) & 0.05511\({}^{\circ}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Orientation control mean squared error (MSE). Figure 24: Error of the orientation control: for the DC motors with no load compared to the desired reference (**a**), for the heliostat compared to the desired reference (**b**), for the DC motors with no load compared to the final reference (**c**), and for the heliostat compared to the final reference (**d**). Figure 23: Orientation control response of the heliostat for the azimuth angle (**a**) and the elevation angle (**b**). The results show an MSE of 0.05371\({}^{\circ}\) and 0.03761\({}^{\circ}\) between the DC motors with no load and the desired reference for the azimuth and elevation angles, respectively (Figure 24a). Besides, there is an MSE of 0.0\({}^{\circ}\) between the final reference values and the angular position of the DC motors with no load (Figure 24c), and an MSE of 0.02352\({}^{\circ}\) and 0.02730\({}^{\circ}\) between the position of the DC motors with no load and the discretized reference for the azimuth and elevation angles, respectively. Therefore, the error signal in the controller is equal to zero when the angular position reaches the final reference value. For the orientation control of the heliostat, the results show an MSE of 0.09577\({}^{\circ}\) and 0.05401\({}^{\circ}\) for the azimuth and elevation angles compared to the desired reference (Figure 24b), which is less than 0.1\({}^{\circ}\) for both axes facing an average wind speed of 6 m/s over the mechanical structure.