## 6 Discussion  
A ground robotic platform has been designed and manufactured, which is equipped with an electrical supply system that combines the use of hydrogen and battery power. Additionally, a control system has been designed to connect both technologies to a DC bus that powers the robotic platform, and safety systems have been implemented to ensure the correct operation of the electrical supply system. Multiple tests were conducted, providing information on the platform's performance and yielding data that allowed its comparison with commercial robotic platforms. The  
Figure 22: Hygrobot operating condition tests for the PEM fuel cell and LiPo battery subsystem: (a) PEM fuel cell temperature tests. (b) PEM fuel cell humidity tests. (c) Battery subsystem temperature tests. (d) Battery subsystem charging/discharging rate tests. proposed, fully assembled platform and its main characteristics are shown in Figure 23 and Table 9.  
In addition, Table 10 allows a comparison of the Hygrobot platform developed by the authors with commercial ground robotic platforms found in the same sector. When comparing the characteristics of Hygrobot with commercial models, it can be observed that the autonomy provided by hybridizing hydrogen and battery power offers noticeable advantages, allowing autonomous activity similar to a full working day (8 h). Additionally, the ability for a quick recharge provides the platform with an option for near-continuous operation, without the need for long waiting times between charges. Regarding the weight of the platform (65 kg), this is still lower than the other platforms studied, making possible the installation of the sensors and actuators needed for its deployment in the working environment or to increase the platform's autonomy by adding an extra tank. Figure 23: Hygrobot: hydrogen–battery hybrid ground robotic platform, as developed by the authors. \begin{table}
\begin{tabular}{l c c c} \hline \hline
**Parameter** & **Value** & **Parameter** & **Value** \\ \hline Weight & 65 kg & Max. torque & 14.80 Nm \\ Dimensions & 870 mm \(\times\) 650 mm \(\times\) 500 mm & Maximum power & 54 W/wheel (\(\times\)6) \\  & & consumption & \\ Power supply system & PEM Fuel Cell + Battery & Load capacity & 50 kg \\ Autonomy & \textgreater{}8 h & Movement control & Remote control \\ Range & 200 m & Protection rating & IP 50 \\ Max. speed & 17 km/h & Start-up time & \textless{}30 s (Temperature 21 \({}^{\circ}\)C) \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Hygrobot technical data. The platform's maximum speed (17 km/h) beats that of the commercial models, and the rate for required power/load capacity is the smallest one (6.48 W/kg). However, the wheel torque is lower, and the tyres' size and diameter prevent the platform from carrying heavy loads on surfaces with very high friction coefficients (such as on mud or sand). Since the working environment for which the robotic platform is designed can be harsh--due to dust, water, plants, etc.--it is noted that commercial models usually offer a high level of protection (IP67 or higher is recommended). In this case, due to the level of development of the platform (TRL 6), an IP50 insulation level was considered sufficient; however, in future works by the authors, in order to be able to commercialize the platform, they will provide the device with a casing that insulates the core components from the external environment. This will guarantee an IP67 protection degree throughout the structure, with particular attention paid to the entry point of the PEM fuel cell oxygenation system. The accumulation of particulate matter inside this can rapidly degrade the PEM fuel cell. Therefore, it is recommended that a PM10 filter or higher filter should be installed at this entry point. Regarding the navigation system, extra equipment like RTK control systems, LiDAR, or similar technologies, combined with the option of a basic remote-control system for short-distance operation can be included in the future.